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.

.cliprepo.yaml

@@ -7,4 +7,13 @@ prompts:
 preset:
   double_app:
     - "app/app/page.tsx"
-    - "app/app/layout.tsx"
+    - "app/app/layout.tsx"
+
+  login:
+    - "app/login/*"
+    - "app/page.tsx"
+    - "app/layout.tsx"
+    - "app/(dashboard)/layout.tsx"
+    - "app/(dashboard)/discover/*"
+    - "app/(dashboard)/roleplay/*"
+    - "proxy.ts"