fixed routings to global game screen. Fixed navbar layouts on the screen. Updated api keys to use private key and added .env file. Configured useGlobalHook to use api from env variable.
Introduce four new screens for global events: GlobalEventsScreen (lists public events and handles joining), GlobalMapScreen (map/list view of event caches with user location via expo-location and markers using react-native-maps), GlobalCacheViewScreen (cache detail view with ability to log discoveries), and GlobalLeaderboardScreen (rankings and recent finds). Screens use existing global hooks and SessionStore for fetching/joining events, caches, finds and for storing current global player context; they include loading/error states and navigation between screens. Also add simple tab components, styling, and refresh actions.