Add SIP plan first slice (3d-5)

Introduce scheduled-investment plans as a schedule-only slice with no
cash, position or NAV side effects. Domain gains SipPolicy: amount
validation (positive, two-decimal, overflow-checked), frequency
parsing/round-trip (weekly/biweekly/monthly), nextTradeDate generating
the next due trade date off the plan anchor with month-end clamping
and weekend roll-forward, plus the isDue/executionNetAmount contract
the future executor will implement (execution itself stays
unimplemented and is marked as such; nothing debits cash in this
slice).

Persistence stores plans in sip_plans with anchor/next trade dates and
sip_plan_idempotencies under the shared replay/conflict contract; the
API exposes POST/GET /funds/{id}/sip/plans behind the bearer token.
The frontend adds a 07/SIP panel (code, amount, frequency select,
plan list with next debit date) and Web tests cover decoding,
validation, in-flight guards and stale completions. Choice note:
first debit is scheduled strictly after the anchor date (creating a
plan today never debits today).

1 files changed, 61 insertions, 0 deletions

diff --git a/tests/FundLab.Domain.Tests/DomainTests.fs b/tests/FundLab.Domain.Tests/DomainTests.fs
index 46516d5..13be13f 100644
--- a/tests/FundLab.Domain.Tests/DomainTests.fs
+++ b/tests/FundLab.Domain.Tests/DomainTests.fs
@@ -560,3 +560,64 @@ module CapitalPolicyTests =
         let overflow = CapitalPolicy.settle CapitalPolicy.cashMaximum 0.01m
 
         Assert.Equal(Error "available cash exceeds database precision", overflow)
+
+module SipPolicyTests =
+
+    open System
+    open Xunit
+    open FundLab.Domain
+
+    let d (year: int) (month: int) (day: int) = DateOnly(year, month, day)
+
+    [<Fact>]
+    let ``sip amount validation rejects non positive or imprecise values`` () =
+        Assert.Equal(Error "sip amount must be positive", SipPolicy.validateAmount 0m)
+        Assert.Equal(Error "sip amount must be positive", SipPolicy.validateAmount -200.00m)
+        Assert.Equal(Error "sip amount exceeds cash precision", SipPolicy.validateAmount 200.005m)
+        Assert.Equal(Ok(), SipPolicy.validateAmount 200.00m)
+
+    [<Fact>]
+    let ``frequency parsing roundtrips through the canonical text`` () =
+        Assert.Equal(Some Weekly, SipPolicy.parseFrequency "weekly")
+        Assert.Equal(Some BiWeekly, SipPolicy.parseFrequency "biweekly")
+        Assert.Equal(Some Monthly, SipPolicy.parseFrequency "monthly")
+        Assert.Equal(None, SipPolicy.parseFrequency "daily")
+        Assert.Equal(None, SipPolicy.parseFrequency null)
+
+        for frequency in [ Weekly; BiWeekly; Monthly ] do
+            Assert.Equal(Some frequency, SipPolicy.parseFrequency (SipPolicy.frequencyText frequency))
+
+    [<Fact>]
+    let ``weekly and biweekly next trade dates step from the anchor`` () =
+        let anchor = d 2026 9 21
+
+        Assert.Equal(d 2026 9 21, SipPolicy.nextTradeDate Weekly anchor (d 2026 9 21))
+        Assert.Equal(d 2026 9 28, SipPolicy.nextTradeDate Weekly anchor (d 2026 9 22))
+        Assert.Equal(d 2026 10 5, SipPolicy.nextTradeDate BiWeekly anchor (d 2026 9 28))
+
+    [<Fact>]
+    let ``next trade dates roll off weekends`` () =
+        let anchor = d 2026 9 21
+
+        Assert.Equal(d 2026 9 28, SipPolicy.nextTradeDate Weekly anchor (d 2026 9 26))
+        Assert.Equal(d 2026 9 28, SipPolicy.nextTradeDate Weekly anchor (d 2026 9 27))
+
+    [<Fact>]
+    let ``monthly next trade date clamps to month end and rolls off weekends`` () =
+        let anchor = d 2026 1 31
+
+        // 2026-01-31 is a Saturday: first run rolls to Monday 02-02
+        Assert.Equal(d 2026 2 2, SipPolicy.nextTradeDate Monthly anchor anchor)
+        // February clamps day 31 to 28 (Saturday) and rolls to Monday 03-02
+        Assert.Equal(d 2026 3 2, SipPolicy.nextTradeDate Monthly anchor (d 2026 2 1))
+        Assert.Equal(d 2026 3 2, SipPolicy.nextTradeDate Monthly anchor (d 2026 2 28))
+        Assert.Equal(d 2026 2 5, SipPolicy.nextTradeDate Monthly (d 2026 1 5) (d 2026 1 20))
+
+    [<Fact>]
+    let ``due flag and net amount define the executor contract without side effects`` () =
+        Assert.True(SipPolicy.isDue (d 2026 9 21) (d 2026 9 21))
+        Assert.True(SipPolicy.isDue (d 2026 9 21) (d 2026 9 28))
+        Assert.False(SipPolicy.isDue (d 2026 9 28) (d 2026 9 21))
+
+        Assert.Equal(Ok 200.00m, SipPolicy.executionNetAmount 200.00m)
+        Assert.Equal(Error "sip amount must be positive", SipPolicy.executionNetAmount 0m)