fix(mobile): correct asset logo path depth and add expo-router app/ routes for web support

- Fix fatal crash: require('../../../assets/logo.png') in LoginScreen and
  WelcomeScreen resolved 3 levels above mobile/src/screens/ — outside the
  mobile/ directory. Changed to ../../assets/logo.png which correctly
  resolves to the existing mobile/assets/logo.png.
- Add expo-router app/ directory (root cause of missing welcome screen and
  web support): app/_layout.tsx, (auth)/, (tabs)/ with all route files
- Add WelcomeScreen.tsx: branded intro screen with feature highlights
- Update LoginScreen/WelcomeScreen to use useRouter() (expo-router style)
- Add react-native-web ~0.20.0 and react-dom 19.2.4 for web channel
- Add expo-device ~7.0.3 (was imported but missing from package.json)
- Remove android.googleServicesFile from app.json (file is gitignored;
  README documents how to restore it for Android FCM builds)
- Add web.bundler: metro and web.output: single to app.json
- Fix aria-hidden to explicit boolean value in WelcomeScreen

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

mobile/package.json

@@ -30,6 +30,7 @@
     "expo-camera": "~17.0.10",
     "expo-constants": "~18.0.13",
     "expo-crypto": "~15.0.8",
+    "expo-device": "~7.0.3",
     "expo-document-picker": "~14.0.8",
     "expo-file-system": "~19.0.21",
     "expo-image-manipulator": "~14.0.8",
@@ -43,7 +44,9 @@
     "expo-status-bar": "~3.0.9",
     "expo-web-browser": "~15.0.10",
     "react": "19.2.4",
+    "react-dom": "19.2.4",
     "react-native": "0.81.5",
+    "react-native-web": "~0.20.0",
     "react-native-safe-area-context": "5.6.0",
     "react-native-screens": "4.16.0"
   },