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.

package.json

@@ -9,7 +9,10 @@
     "lint": "eslint"
   },
   "dependencies": {
+    "@apollo/client": "^4.1.9",
+    "@apollo/experimental-nextjs-app-support": "^0.14.5",
     "@tailwindcss/cli": "^4.3.0",
+    "graphql": "^16.14.0",
     "lucide-react": "^1.16.0",
     "next": "16.2.6",
     "react": "19.2.4",