integrate backend Google OAuth and set up avatar media proxy

- Implement the full login and onboarding workflow to handle name, handle, and avatar.

- Rewrite avatar asset URLs to route through the self-hosted media service.

- Add Next.js rewrites configuration to proxy media requests directly to the FastAPI backend.

providers/ApolloProvider.tsx

@@ -0,0 +1,32 @@
+"use client";
+
+import React from "react";
+import { HttpLink } from "@apollo/client";
+import {
+  ApolloClient,
+  ApolloNextAppProvider,
+  InMemoryCache,
+} from "@apollo/experimental-nextjs-app-support";
+
+// 创建一个初始化 Client 的函数
+function makeClient() {
+  const httpLink = new HttpLink({
+    uri: process.env.NEXT_PUBLIC_GRAPHQL_URL || "http://localhost:8000/graphql",
+    // 确保跨域请求自动带上 Cookie
+    credentials: "include", 
+  });
+
+  return new ApolloClient({
+    cache: new InMemoryCache(),
+    link: httpLink,
+  });
+}
+
+// 导出我们的包装组件
+export function GraphqlProvider({ children }: { children: React.ReactNode }) {
+  return (
+    <ApolloNextAppProvider makeClient={makeClient}>
+      {children}
+    </ApolloNextAppProvider>
+  );
+}

providers/index.tsx

@@ -0,0 +1,13 @@
+"use client";
+
+import React from "react";
+import { GraphqlProvider } from "./ApolloProvider";
+
+export function Providers({ children }: { children: React.ReactNode }) {
+  return (
+    <GraphqlProvider>
+      {/* 在这里可以继续嵌套其他全局 Provider */}
+      {children}
+    </GraphqlProvider>
+  );
+}