refactor: remove legacy frontend code and implement new Next.js structure

- Deleted the old Register page and utility functions.
- Removed Tailwind CSS configuration and Vite configuration files.
- Added a new script for starting a single container with FastAPI and Next.js.
- Updated README to reflect the current status of the Next.js frontend.
- Implemented new login and registration API routes with improved error handling.
- Refactored frontend API calls to use the new proxy structure.
- Enhanced error handling in API response processing.
- Updated components to align with the new API endpoints and structure.

web/src/app/frontend-api/auth/me/route.ts

@@ -0,0 +1,57 @@
+import { cookies } from "next/headers";
+import { NextResponse } from "next/server";
+
+import {
+  SESSION_COOKIE_NAME,
+  buildBackendUrl
+} from "@/lib/api/config";
+import {
+  getResponseErrorMessage,
+  isRecord,
+  readResponsePayload
+} from "@/lib/api/response";
+
+export async function GET() {
+  const token = cookies().get(SESSION_COOKIE_NAME)?.value;
+
+  if (!token) {
+    return NextResponse.json({ detail: "Unauthorized" }, { status: 401 });
+  }
+
+  let response: Response;
+  try {
+    response = await fetch(buildBackendUrl("/auth/me"), {
+      headers: {
+        Authorization: `Bearer ${token}`
+      },
+      cache: "no-store"
+    });
+  } catch {
+    return NextResponse.json(
+      { detail: "Backend API is unavailable." },
+      { status: 502 }
+    );
+  }
+
+  const payload = await readResponsePayload(response);
+
+  if (response.status === 401) {
+    cookies().delete(SESSION_COOKIE_NAME);
+  }
+
+  if (!response.ok) {
+    return NextResponse.json(
+      { detail: getResponseErrorMessage(payload, "获取当前用户失败") },
+      { status: response.status }
+    );
+  }
+
+  if (!isRecord(payload)) {
+    return NextResponse.json(
+      { detail: "Backend returned an invalid auth response." },
+      { status: 502 }
+    );
+  }
+
+  return NextResponse.json(payload, { status: response.status });
+}