feat(email): 初始化自建邮箱 MVP

- 新增 Go + SQLite 后端，支持登录、域名、邮箱、别名、联系人、规则、统计与邮件收发。
- 新增 Webmail 前端，支持多邮箱切换、邮件列表/阅读/写信、附件、搜索、主题切换与个人中心。
- 新增 Docker Compose 部署骨架，补充 Postfix、Dovecot、OpenDKIM、Nginx 配置与部署说明。

apps/web/src/main.tsx

@@ -0,0 +1,31 @@
+import React from "react"
+import ReactDOM from "react-dom/client"
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query"
+import { Navigate, RouterProvider, createBrowserRouter } from "react-router-dom"
+import { Toaster } from "@/components/ui/toaster"
+import { ProtectedLayout } from "@/components/protected-layout"
+import { LoginPage } from "@/pages/login"
+import { MailPage } from "@/pages/mail"
+import { AdminPage } from "@/pages/admin"
+import { ProfilePage } from "@/pages/profile"
+import "./index.css"
+
+const queryClient = new QueryClient({ defaultOptions: { queries: { refetchOnWindowFocus: false, staleTime: 10_000 } } })
+const router = createBrowserRouter([
+  { path: "/login", element: <LoginPage /> },
+  { path: "/", element: <ProtectedLayout />, children: [
+    { index: true, element: <Navigate to="/mail" replace /> },
+    { path: "mail", element: <MailPage /> },
+    { path: "profile", element: <ProfilePage /> },
+    { path: "admin", element: <AdminPage /> },
+  ] },
+])
+
+ReactDOM.createRoot(document.getElementById("root")!).render(
+  <React.StrictMode>
+    <QueryClientProvider client={queryClient}>
+      <RouterProvider router={router} />
+      <Toaster />
+    </QueryClientProvider>
+  </React.StrictMode>,
+)