feat(api,web): 模拟认购订单创建/读取，幂等与预留现金（3d-1）

- API: POST/GET /api/funds/{fundId}/orders，advisory lock + 行级锁事务预留现金，
  幂等键重放/冲突/校验/目录缺失错误码齐全，基金响应新增 reservedCash
- Persistence: subscription_orders 与幂等表 + 保留现金列迁移
- Web: 认购表单与待确认订单列表（已提交·待确认），失败重试复用幂等键，
  token 轮换隔离延迟响应
- 测试: API 41（含并发不足/回滚/真实宿主重启回归）、Web 17、Domain 19；
  浏览器 QA 58 项全过

2 files changed, 430 insertions, 4 deletions

diff --git a/src/FundLab.Api/App.fs b/src/FundLab.Api/App.fs
index f61e760..a2aa271 100644
--- a/src/FundLab.Api/App.fs
+++ b/src/FundLab.Api/App.fs
@@ -22,9 +22,23 @@ type FundApiResponse =
         initialUnitNav: string
         isSynthetic: bool
         availableCash: string
+        reservedCash: string
         status: string
     }
 
+type SubscriptionOrderApiResponse =
+    {
+        id: Guid
+        fundId: Guid
+        fundCode: string
+        amount: string
+        feeAmount: string
+        reservedTotal: string
+        status: string
+        submittedAt: string
+        isSynthetic: bool
+    }
+
 type ApiErrorResponse =
     {
         error: string
@@ -86,9 +100,23 @@ module App =
             initialUnitNav = unitNavText fund.InitialUnitNav
             isSynthetic = fund.IsSynthetic
             availableCash = cashText fund.AvailableCash
+            reservedCash = cashText fund.ReservedCash
             status = fund.Status
         }
 
+    let private orderResponse (order: SubscriptionOrderRecord) : SubscriptionOrderApiResponse =
+        {
+            id = order.Id
+            fundId = order.FundId
+            fundCode = order.FundCode
+            amount = cashText order.Amount
+            feeAmount = cashText order.FeeAmount
+            reservedTotal = cashText order.ReservedTotal
+            status = order.Status
+            submittedAt = timestampText order.SubmittedAt
+            isSynthetic = order.IsSynthetic
+        }
+
     let private errorResponse status error message : HttpHandler =
         setStatusCode status
         >=> json ({
@@ -148,6 +176,30 @@ module App =
         with
         | :? JsonException -> Error "request body must be valid JSON"
 
+    let private parseOrderCommand (body: string) =
+        try
+            use document = JsonDocument.Parse(body)
+            let root = document.RootElement
+
+            if root.ValueKind <> JsonValueKind.Object then
+                Error "request body must be a JSON object"
+            else
+                match tryStringProperty root "fundCode", tryStringProperty root "amount", tryStringProperty root "feeAmount" with
+                | Some fundCode, Some amountText, Some feeAmountText ->
+                    match tryDecimal "amount" amountText, tryDecimal "feeAmount" feeAmountText with
+                    | Ok amount, Ok feeAmount ->
+                        Ok {
+                            FundCode = fundCode
+                            Amount = amount
+                            FeeAmount = feeAmount
+                        }
+                    | Error message, _
+                    | _, Error message -> Error message
+                | _ ->
+                    Error "fundCode, amount and feeAmount are required"
+        with
+        | :? JsonException -> Error "request body must be valid JSON"
+
     let private invokeHandler handler next ctx = handler next ctx
 
     let private unauthorized : HttpHandler =
@@ -216,6 +268,55 @@ module App =
                 with _ ->
                     errorResponse 500 "PERSISTENCE_ERROR" "fund persistence failed" next ctx
 
+    let private createOrder (repository: FundRepository) (fundIdText: string) : HttpHandler =
+        fun next ctx ->
+            task {
+                match Guid.TryParse fundIdText with
+                | false, _ ->
+                    return! invokeHandler (errorResponse 400 "INVALID_FUND_ID" "fund id must be a UUID") next ctx
+                | true, fundId ->
+                    use reader = new StreamReader(ctx.Request.Body)
+                    let! body = reader.ReadToEndAsync()
+                    let idempotencyKey = ctx.Request.Headers["Idempotency-Key"].ToString()
+
+                    match parseOrderCommand body with
+                    | Error message ->
+                        return! invokeHandler (errorResponse 400 "INVALID_ORDER_REQUEST" message) next ctx
+                    | Ok command ->
+                        try
+                            match repository.CreateSubscriptionOrder(idempotencyKey, fundId, command) with
+                            | SubscriptionOrderWriteResult.OrderCreated order ->
+                                return! invokeHandler (setStatusCode 201 >=> json (orderResponse order)) next ctx
+                            | SubscriptionOrderWriteResult.OrderReplayed order ->
+                                return! invokeHandler (json (orderResponse order)) next ctx
+                            | SubscriptionOrderWriteResult.OrderIdempotencyConflict ->
+                                return! invokeHandler (errorResponse 409 "IDEMPOTENCY_CONFLICT" "idempotency key was used with a different request") next ctx
+                            | SubscriptionOrderWriteResult.OrderInvalid message ->
+                                return! invokeHandler (errorResponse 400 "INVALID_ORDER_REQUEST" message) next ctx
+                            | SubscriptionOrderWriteResult.OrderFundNotFound ->
+                                return! invokeHandler (errorResponse 404 "FUND_NOT_FOUND" "fund was not found") next ctx
+                            | SubscriptionOrderWriteResult.OrderInstrumentNotFound ->
+                                return! invokeHandler (errorResponse 404 "INSTRUMENT_NOT_FOUND" "fund code was not found in the instrument catalog") next ctx
+                            | SubscriptionOrderWriteResult.OrderInsufficientFunds ->
+                                return! invokeHandler (errorResponse 409 "INSUFFICIENT_FUNDS" "available cash is not enough to reserve the amount plus fee") next ctx
+                        with _ ->
+                            return! invokeHandler (errorResponse 500 "PERSISTENCE_ERROR" "order persistence failed") next ctx
+            }
+
+    let private getOrders (repository: FundRepository) (fundIdText: string) : HttpHandler =
+        fun next ctx ->
+            match Guid.TryParse fundIdText with
+            | false, _ -> errorResponse 400 "INVALID_FUND_ID" "fund id must be a UUID" next ctx
+            | true, fundId ->
+                try
+                    match repository.GetFund fundId with
+                    | None -> errorResponse 404 "FUND_NOT_FOUND" "fund was not found" next ctx
+                    | Some _ ->
+                        let orders = repository.GetSubscriptionOrders fundId
+                        json (orders |> List.map orderResponse) next ctx
+                with _ ->
+                    errorResponse 500 "PERSISTENCE_ERROR" "order persistence failed" next ctx
+
     let private marketDataError (failure: MarketDataFailure) : HttpHandler =
         let status, error, message =
             match failure with
@@ -311,6 +412,8 @@ module App =
             [
                 GET >=> route "/portfolio/summary" >=> emptyPortfolio
                 POST >=> route "/funds" >=> createFund repository
+                POST >=> routef "/funds/%s/orders" (createOrder repository)
+                GET >=> routef "/funds/%s/orders" (getOrders repository)
                 GET >=> routef "/funds/%s" (getFund repository)
             ]
             @ (marketData |> Option.map marketDataRoutes |> Option.defaultValue [])
diff --git a/src/FundLab.Api/Persistence.fs b/src/FundLab.Api/Persistence.fs
index e48d9b1..88c0350 100644
--- a/src/FundLab.Api/Persistence.fs
+++ b/src/FundLab.Api/Persistence.fs
@@ -28,6 +28,7 @@ type FundRecord =
         InitialUnitNav: decimal
         IsSynthetic: bool
         AvailableCash: decimal
+        ReservedCash: decimal
         Status: string
     }
 
@@ -37,6 +38,36 @@ type FundWriteResult =
     | IdempotencyConflict
     | Invalid of string
 
+[<CLIMutable>]
+type SubscriptionOrderCommand =
+    {
+        FundCode: string
+        Amount: decimal
+        FeeAmount: decimal
+    }
+
+type SubscriptionOrderRecord =
+    {
+        Id: Guid
+        FundId: Guid
+        FundCode: string
+        Amount: decimal
+        FeeAmount: decimal
+        ReservedTotal: decimal
+        Status: string
+        SubmittedAt: DateTimeOffset
+        IsSynthetic: bool
+    }
+
+type SubscriptionOrderWriteResult =
+    | OrderCreated of SubscriptionOrderRecord
+    | OrderReplayed of SubscriptionOrderRecord
+    | OrderIdempotencyConflict
+    | OrderInvalid of string
+    | OrderFundNotFound
+    | OrderInstrumentNotFound
+    | OrderInsufficientFunds
+
 type FundRepository(connectionString: string) =
     let cashMaximum = 999999999999999999.99m
     let unitNavMaximum = 99999999999999999999.99999999m
@@ -92,6 +123,28 @@ type FundRepository(connectionString: string) =
 
         CREATE INDEX IF NOT EXISTS fund_nav_observations_date_idx
             ON fund_nav_observations (instrument_code, nav_date);
+
+        ALTER TABLE funds ADD COLUMN IF NOT EXISTS reserved_cash numeric(20, 2) NOT NULL DEFAULT 0;
+
+        CREATE TABLE IF NOT EXISTS subscription_orders (
+            id uuid PRIMARY KEY,
+            fund_id uuid NOT NULL REFERENCES funds(id),
+            fund_code text NOT NULL,
+            amount numeric(20, 2) NOT NULL CHECK (amount > 0),
+            fee_amount numeric(20, 2) NOT NULL CHECK (fee_amount > 0),
+            reserved_total numeric(20, 2) NOT NULL CHECK (reserved_total > 0),
+            status text NOT NULL,
+            is_synthetic boolean NOT NULL,
+            submitted_at timestamptz NOT NULL DEFAULT now()
+        );
+
+        CREATE TABLE IF NOT EXISTS subscription_order_idempotencies (
+            idempotency_key text PRIMARY KEY,
+            request_hash text NOT NULL,
+            order_id uuid NOT NULL REFERENCES subscription_orders(id),
+            fund_id uuid NOT NULL REFERENCES funds(id),
+            created_at timestamptz NOT NULL DEFAULT now()
+        );
         """
 
     let statusText status =
@@ -109,6 +162,7 @@ type FundRepository(connectionString: string) =
             InitialUnitNav = fund.InitialUnitNav
             IsSynthetic = fund.IsSynthetic
             AvailableCash = fund.AvailableCash
+            ReservedCash = fund.FrozenCash
             Status = statusText fund.Status
         }
 
@@ -121,7 +175,8 @@ type FundRepository(connectionString: string) =
             InitialUnitNav = reader.GetDecimal(4)
             IsSynthetic = reader.GetBoolean(5)
             AvailableCash = reader.GetDecimal(6)
-            Status = reader.GetString(7)
+            ReservedCash = reader.GetDecimal(7)
+            Status = reader.GetString(8)
         }
 
     let dateTimeOffsetFromReader (reader: DbDataReader) index =
@@ -189,7 +244,7 @@ type FundRepository(connectionString: string) =
                 transaction
                 """
                 SELECT id, name, currency, initial_cash, initial_unit_nav,
-                       is_synthetic, available_cash, status
+                       is_synthetic, available_cash, reserved_cash, status
                 FROM funds
                 WHERE id = @fund_id
                 """
@@ -219,10 +274,10 @@ type FundRepository(connectionString: string) =
                 """
                 INSERT INTO funds
                     (id, name, currency, initial_cash, initial_unit_nav,
-                     is_synthetic, available_cash, status)
+                     is_synthetic, available_cash, reserved_cash, status)
                 VALUES
                     (@id, @name, @currency, @initial_cash, @initial_unit_nav,
-                     @is_synthetic, @available_cash, @status)
+                     @is_synthetic, @available_cash, @reserved_cash, @status)
                 """
 
         addParameter command "id" NpgsqlDbType.Uuid (box fund.Id) |> ignore
@@ -232,6 +287,7 @@ type FundRepository(connectionString: string) =
         addParameter command "initial_unit_nav" NpgsqlDbType.Numeric (box fund.InitialUnitNav) |> ignore
         addParameter command "is_synthetic" NpgsqlDbType.Boolean (box fund.IsSynthetic) |> ignore
         addParameter command "available_cash" NpgsqlDbType.Numeric (box fund.AvailableCash) |> ignore
+        addParameter command "reserved_cash" NpgsqlDbType.Numeric (box fund.FrozenCash) |> ignore
         addParameter command "status" NpgsqlDbType.Text (box (statusText fund.Status)) |> ignore
         command.ExecuteNonQuery() |> ignore
 
@@ -250,6 +306,121 @@ type FundRepository(connectionString: string) =
         addParameter command "fund_id" NpgsqlDbType.Uuid (box fundId) |> ignore
         command.ExecuteNonQuery() |> ignore
 
+    let orderStatusText = "submitted"
+
+    let orderRecordFromReader (reader: DbDataReader) : SubscriptionOrderRecord =
+        {
+            Id = reader.GetGuid(0)
+            FundId = reader.GetGuid(1)
+            FundCode = reader.GetString(2)
+            Amount = reader.GetDecimal(3)
+            FeeAmount = reader.GetDecimal(4)
+            ReservedTotal = reader.GetDecimal(5)
+            Status = reader.GetString(6)
+            IsSynthetic = reader.GetBoolean(7)
+            SubmittedAt = reader.GetFieldValue<DateTimeOffset>(8)
+        }
+
+    let findOrder connection transaction orderId =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                """
+                SELECT id, fund_id, fund_code, amount, fee_amount,
+                       reserved_total, status, is_synthetic, submitted_at
+                FROM subscription_orders
+                WHERE id = @order_id
+                """
+
+        addParameter command "order_id" NpgsqlDbType.Uuid (box orderId) |> ignore
+
+        use reader = command.ExecuteReader()
+        if reader.Read() then Some(orderRecordFromReader reader) else None
+
+    let findOrderIdempotency connection transaction key =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                "SELECT request_hash, fund_id, order_id FROM subscription_order_idempotencies WHERE idempotency_key = @idempotency_key"
+
+        addParameter command "idempotency_key" NpgsqlDbType.Text (box key) |> ignore
+
+        use reader = command.ExecuteReader()
+        if reader.Read() then
+            Some(reader.GetString(0), reader.GetGuid(1), reader.GetGuid(2))
+        else
+            None
+
+    let instrumentExists connection transaction code =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                "SELECT 1 FROM instruments WHERE code = @code"
+
+        addParameter command "code" NpgsqlDbType.Text (box code) |> ignore
+
+        use reader = command.ExecuteReader()
+        reader.Read()
+
+    let lockFundForOrder connection transaction fundId =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                "SELECT is_synthetic FROM funds WHERE id = @fund_id FOR UPDATE"
+
+        addParameter command "fund_id" NpgsqlDbType.Uuid (box fundId) |> ignore
+
+        use reader = command.ExecuteReader()
+        if reader.Read() then Some(reader.GetBoolean(0)) else None
+
+    let insertSubscriptionOrder connection transaction (order: SubscriptionOrderRecord) =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                """
+                INSERT INTO subscription_orders
+                    (id, fund_id, fund_code, amount, fee_amount,
+                     reserved_total, status, is_synthetic)
+                VALUES
+                    (@id, @fund_id, @fund_code, @amount, @fee_amount,
+                     @reserved_total, @status, @is_synthetic)
+                RETURNING submitted_at
+                """
+
+        addParameter command "id" NpgsqlDbType.Uuid (box order.Id) |> ignore
+        addParameter command "fund_id" NpgsqlDbType.Uuid (box order.FundId) |> ignore
+        addParameter command "fund_code" NpgsqlDbType.Text (box order.FundCode) |> ignore
+        addParameter command "amount" NpgsqlDbType.Numeric (box order.Amount) |> ignore
+        addParameter command "fee_amount" NpgsqlDbType.Numeric (box order.FeeAmount) |> ignore
+        addParameter command "reserved_total" NpgsqlDbType.Numeric (box order.ReservedTotal) |> ignore
+        addParameter command "status" NpgsqlDbType.Text (box order.Status) |> ignore
+        addParameter command "is_synthetic" NpgsqlDbType.Boolean (box order.IsSynthetic) |> ignore
+
+        use reader = command.ExecuteReader()
+        reader.Read() |> ignore
+        reader.GetFieldValue<DateTimeOffset>(0)
+
+    let insertOrderIdempotency connection transaction key requestHash orderId fundId =
+        use command =
+            commandWithTransaction
+                connection
+                transaction
+                """
+                INSERT INTO subscription_order_idempotencies (idempotency_key, request_hash, order_id, fund_id)
+                VALUES (@idempotency_key, @request_hash, @order_id, @fund_id)
+                """
+
+        addParameter command "idempotency_key" NpgsqlDbType.Text (box key) |> ignore
+        addParameter command "request_hash" NpgsqlDbType.Text (box requestHash) |> ignore
+        addParameter command "order_id" NpgsqlDbType.Uuid (box orderId) |> ignore
+        addParameter command "fund_id" NpgsqlDbType.Uuid (box fundId) |> ignore
+        command.ExecuteNonQuery() |> ignore
+
     let upsertInstrument connection transaction (payload: MarketDataSearchPayload) payloadHash (instrument: MarketDataInstrument) =
         use command =
             commandWithTransaction
@@ -371,6 +542,43 @@ type FundRepository(connectionString: string) =
         else
             Ok()
 
+    let orderRequestHash (fundId: Guid) (command: SubscriptionOrderCommand) =
+        let invariant = CultureInfo.InvariantCulture
+        let encoded (value: string) = sprintf "%d:%s" value.Length value
+        let fundCode = if isNull command.FundCode then "" else command.FundCode
+        let payload =
+            String.concat
+                "|"
+                [
+                    "subscription-order"
+                    encoded (fundId.ToString("D"))
+                    encoded fundCode
+                    (encoded (command.Amount.ToString("G29", invariant)))
+                    (encoded (command.FeeAmount.ToString("G29", invariant)))
+                ]
+
+        Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(payload)))
+
+    let validateOrderCommand (command: SubscriptionOrderCommand) =
+        if String.IsNullOrWhiteSpace command.FundCode then
+            Error "fund code cannot be empty"
+        elif command.Amount <= 0m then
+            Error "amount must be positive"
+        elif command.FeeAmount <= 0m then
+            Error "fee amount must be positive"
+        elif Decimal.Round(command.Amount, 2) <> command.Amount then
+            Error "amount exceeds cash precision"
+        elif Decimal.Round(command.FeeAmount, 2) <> command.FeeAmount then
+            Error "fee amount exceeds cash precision"
+        elif command.Amount > cashMaximum then
+            Error "amount exceeds database precision"
+        elif command.FeeAmount > cashMaximum then
+            Error "fee amount exceeds database precision"
+        elif command.Amount + command.FeeAmount > cashMaximum then
+            Error "reserved total exceeds database precision"
+        else
+            Ok()
+
     let ledgerErrorMessage error =
         match error with
         | InvalidIdentifier label -> sprintf "%s is invalid" label
@@ -552,3 +760,118 @@ type FundRepository(connectionString: string) =
                         ()
 
                     raise error
+
+    member _.CreateSubscriptionOrder(idempotencyKey: string, fundId: Guid, command: SubscriptionOrderCommand) =
+        if String.IsNullOrWhiteSpace idempotencyKey then
+            OrderInvalid "idempotency key cannot be empty"
+        else
+            match validateOrderCommand command with
+            | Error message -> OrderInvalid message
+            | Ok() ->
+                let fingerprint = orderRequestHash fundId command
+                let reservedTotal = command.Amount + command.FeeAmount
+                use connection = new NpgsqlConnection(connectionString)
+                connection.Open()
+                use transaction = connection.BeginTransaction(IsolationLevel.ReadCommitted)
+
+                try
+                    use lockCommand =
+                        commandWithTransaction
+                            connection
+                            (Some transaction)
+                            "SELECT pg_advisory_xact_lock(hashtext(@lock_key))"
+
+                    addParameter lockCommand "lock_key" NpgsqlDbType.Text (box idempotencyKey) |> ignore
+                    lockCommand.ExecuteNonQuery() |> ignore
+
+                    match findOrderIdempotency connection (Some transaction) idempotencyKey with
+                    | Some(existingHash, existingFundId, orderId)
+                        when existingHash = fingerprint && existingFundId = fundId ->
+                        match findOrder connection (Some transaction) orderId with
+                        | Some order ->
+                            transaction.Commit()
+                            OrderReplayed order
+                        | None ->
+                            transaction.Rollback()
+                            OrderInvalid "idempotency record references a missing order"
+                    | Some _ ->
+                        transaction.Rollback()
+                        OrderIdempotencyConflict
+                    | None ->
+                        match lockFundForOrder connection (Some transaction) fundId with
+                        | None ->
+                            transaction.Rollback()
+                            OrderFundNotFound
+                        | Some isSynthetic ->
+                            if instrumentExists connection (Some transaction) command.FundCode then
+                                use cashCommand =
+                                    commandWithTransaction
+                                        connection
+                                        (Some transaction)
+                                        """
+                                        UPDATE funds
+                                        SET available_cash = available_cash - @reserved_total,
+                                            reserved_cash = reserved_cash + @reserved_total
+                                        WHERE id = @fund_id AND available_cash >= @reserved_total
+                                        """
+
+                                addParameter cashCommand "reserved_total" NpgsqlDbType.Numeric (box reservedTotal) |> ignore
+                                addParameter cashCommand "fund_id" NpgsqlDbType.Uuid (box fundId) |> ignore
+
+                                if cashCommand.ExecuteNonQuery() = 0 then
+                                    transaction.Rollback()
+                                    OrderInsufficientFunds
+                                else
+                                    let order: SubscriptionOrderRecord =
+                                        {
+                                            Id = Guid.NewGuid()
+                                            FundId = fundId
+                                            FundCode = command.FundCode
+                                            Amount = command.Amount
+                                            FeeAmount = command.FeeAmount
+                                            ReservedTotal = reservedTotal
+                                            Status = orderStatusText
+                                            SubmittedAt = DateTimeOffset.UnixEpoch
+                                            IsSynthetic = isSynthetic
+                                        }
+
+                                    let submittedAt = insertSubscriptionOrder connection (Some transaction) order
+                                    insertOrderIdempotency connection (Some transaction) idempotencyKey fingerprint order.Id fundId
+                                    transaction.Commit()
+                                    OrderCreated { order with SubmittedAt = submittedAt }
+                            else
+                                transaction.Rollback()
+                                OrderInstrumentNotFound
+                with error ->
+                    try
+                        transaction.Rollback()
+                    with _ ->
+                        ()
+
+                    raise error
+
+    member _.GetSubscriptionOrders(fundId: Guid) =
+        use connection = new NpgsqlConnection(connectionString)
+        connection.Open()
+
+        use command =
+            commandWithTransaction
+                connection
+                None
+                """
+                SELECT id, fund_id, fund_code, amount, fee_amount,
+                       reserved_total, status, is_synthetic, submitted_at
+                FROM subscription_orders
+                WHERE fund_id = @fund_id
+                ORDER BY submitted_at DESC, id
+                """
+
+        addParameter command "fund_id" NpgsqlDbType.Uuid (box fundId) |> ignore
+
+        use reader = command.ExecuteReader()
+        let records = ResizeArray<SubscriptionOrderRecord>()
+
+        while reader.Read() do
+            records.Add(orderRecordFromReader reader)
+
+        records |> Seq.toList