OAuth routes (Google/Facebook/Apple) + Android web export

- Google OAuth: /auth/google + /auth/google/callback
- Facebook OAuth: /auth/facebook + /auth/facebook/callback
- Apple Sign In placeholder
- Expo web export in mobile/dist/
- passport, passport-google-oauth20, passport-facebook installed

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mobile/package.json

@@ -4,8 +4,8 @@
   "main": "index.ts",
   "scripts": {
     "start": "expo start",
-    "android": "expo start --android",
-    "ios": "expo start --ios",
+    "android": "expo run:android",
+    "ios": "expo run:ios",
     "web": "expo start --web",
     "export:web": "expo export --platform web",
     "lint": "expo lint"