feat: 迁移前端构建从 Bun fullstack 到 Vite

前端性能问题根因在于 Bun bundler 无法有效 code split、CSS
tree-shake 和产出优化的前端资源。经多轮 Bun 原生优化尝试
均无明显效果后，决定将前端构建迁回 Vite。

主要变更：

- 前端构建：从 Bun HTML import bundling 切换为 Vite build
  （Rolldown code splitting、vendor chunk、CSS 优化）
- 开发模式：从 Bun fullstack 单进程 HMR 切换为 Vite dev
  server + Bun API server 双进程（:5173 + :3000）
- 生产构建：三步流水线（Vite build → code generation →
  Bun compile），通过 `import with { type: "file" }` 嵌入前端资源
- 静态资源服务：从 Bun HTML import manifest 切换为自定义
  serveStaticAsset 函数，支持 SPA fallback 和正确的 Cache-Control
- Server 接口：BootstrapOptions 和 StartServerOptions 增加
  staticAssets? 可选参数
- 文档更新：DEVELOPMENT.md 和 README.md 反映新的开发模式，
  主 specs 同步 delta 变更

新增能力：
- static-asset-embedding: 构建时资源扫描与 code generation、
  运行时静态资源服务
- vite-frontend-bundling: Vite 构建配置、code splitting 策略、
  CSS 处理

src/server/server.ts

@@ -1,33 +1,36 @@
 import type { RuntimeMode } from "../shared/api";
 import type { ProbeStore } from "./checker/store";
 import type { RuntimeConfig } from "./config";
+import type { StaticAssets } from "./static";
 
-import homepage from "../web/index.html";
 import { createApiError, jsonResponse } from "./helpers";
 import { handleDashboard } from "./routes/dashboard";
 import { handleHealth } from "./routes/health";
 import { handleHistory } from "./routes/history";
 import { handleMeta } from "./routes/meta";
 import { handleMetrics } from "./routes/metrics";
+import { serveStaticAsset } from "./static";
 
 export interface StartServerOptions {
   config: RuntimeConfig;
   mode: RuntimeMode;
+  staticAssets?: StaticAssets;
   store: ProbeStore;
 }
 
 export function startServer(options: StartServerOptions) {
-  const { config, mode, store } = options;
+  const { config, mode, staticAssets, store } = options;
 
   const server = Bun.serve({
-    development: mode === "development" ? { console: true, hmr: true } : false,
-    fetch() {
-      return new Response("Not found", { status: 404 });
+    fetch(req) {
+      if (staticAssets) {
+        return serveStaticAsset(new URL(req.url).pathname, staticAssets);
+      }
+      return new Response("Frontend is served by Vite dev server on :5173", { status: 404 });
     },
     hostname: config.host,
     port: config.port,
     routes: {
-      "/*": homepage,
       "/api/*": () => jsonResponse(createApiError("API route not found", 404), { mode, status: 404 }),
       "/api/dashboard": {
         GET: (req) => handleDashboard(new URL(req.url), store, mode),