chore(frontend): shadcn-svelte / Tailwind / layerchart 工具链初始化

[变更性质]
本轮为维护性依赖与配置初始化，不改变业务页面（页面迁移见后续提交）。

[维护内容]
按 Leader 返工指令，前端 UI 组件库全量迁移 shadcn-svelte，图表渲染
从 echarts 换为 layerchart，需要一次性引入配套依赖与构建配置。

[实现方案]
package.json/pnpm-lock.yaml：tailwindcss@4、@tailwindcss/vite、
tw-animate-css、shadcn-svelte、bits-ui、tailwind-variants、clsx、
tailwind-merge、@lucide/svelte、layerchart、@fontsource-variable/inter
与 @types/node；echarts 保留至页面迁移完成后移除。pnpm-workspace.yaml
声明 allowBuilds（esbuild、@tailwindcss/oxide）。components.json 采用
mira preset，别名 $lib。tsconfig 新增 $lib paths；vite.config.ts 加入
tailwindcss 插件、$lib alias（vitest 需要）与 test 环境配置。
src/lib/components/ 为 shadcn 生成的 UI 组件源码（button/input/label/
card/badge/alert/select/table/tabs/separator/chart），src/lib/utils.ts
为 cn 工具。app.css 引入 tailwind 与 shadcn CSS 变量并调整为 teal
主题（primary #0f766e、radius 0.375rem、双主题 chart-1..5），保留
legacy 选择器（banner/beat/table.data/metric 等），mobileCss.test.ts
依赖其语义断言。

[影响范围]
构建链与主题变量；后续页面提交逐步消费这些组件，npm run check/test/
build 已全绿验证。

1 files changed, 45 insertions, 0 deletions

diff --git a/frontend/src/lib/components/ui/select/select-content.svelte b/frontend/src/lib/components/ui/select/select-content.svelte
new file mode 100644
index 0000000..3ec8408
--- /dev/null
+++ b/frontend/src/lib/components/ui/select/select-content.svelte
@@ -0,0 +1,45 @@
+<script lang="ts">
+	import { Select as SelectPrimitive } from "bits-ui";
+	import { cn, type WithoutChild } from "$lib/utils.js";
+	import type { WithoutChildrenOrChild } from "$lib/utils.js";
+	import SelectPortal from "./select-portal.svelte";
+	import SelectScrollDownButton from "./select-scroll-down-button.svelte";
+	import SelectScrollUpButton from "./select-scroll-up-button.svelte";
+	import type { ComponentProps } from "svelte";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		sideOffset = 4,
+		portalProps,
+		children,
+		preventScroll = true,
+		...restProps
+	}: WithoutChild<SelectPrimitive.ContentProps> & {
+		portalProps?: WithoutChildrenOrChild<ComponentProps<typeof SelectPortal>>;
+	} = $props();
+</script>
+
+<SelectPortal {...portalProps}>
+	<SelectPrimitive.Content
+		bind:ref
+		{sideOffset}
+		{preventScroll}
+		data-slot="select-content"
+		class={cn(
+			"bg-popover text-popover-foreground data-open:animate-in data-closed:animate-out data-closed:fade-out-0 data-open:fade-in-0 data-closed:zoom-out-95 data-open:zoom-in-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2 ring-foreground/10 min-w-32 rounded-lg shadow-md ring-1 duration-100 relative z-50 max-h-(--bits-select-content-available-height) origin-(--bits-select-content-transform-origin) overflow-x-hidden overflow-y-auto",
+			className
+		)}
+		{...restProps}
+	>
+		<SelectScrollUpButton />
+		<SelectPrimitive.Viewport
+			class={cn(
+				"h-(--bits-select-anchor-height) w-full min-w-(--bits-select-anchor-width) scroll-my-1"
+			)}
+		>
+			{@render children?.()}
+		</SelectPrimitive.Viewport>
+		<SelectScrollDownButton />
+	</SelectPrimitive.Content>
+</SelectPortal>