Migrate backend from Lovable Cloud to own Supabase (EDU project)

- Point .env + supabase/config.toml at EDU (qgmcpounpkgsjlwosjdi)
- Replace Lovable Google-OAuth shim with native supabase.auth.signInWithOAuth
- Remove src/integrations/lovable and @lovable.dev/cloud-auth-js dependency
- Drop .lovable metadata; gitignore supabase/.temp

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -13,7 +13,6 @@
   },
   "dependencies": {
     "@hookform/resolvers": "^5.2.2",
-    "@lovable.dev/cloud-auth-js": "^1.1.2",
     "@radix-ui/react-accordion": "^1.2.12",
     "@radix-ui/react-alert-dialog": "^1.1.15",
     "@radix-ui/react-aspect-ratio": "^1.1.8",