feat(service): add foreground service for background message sync

Implement Android foreground service to keep app alive in background for real-time message sync:
- Add withForegroundService expo config plugin for notification channel setup
- Add BackgroundSyncManager with REALTIME, BATTERY_SAVER, and DISABLED modes
- Add ForegroundServiceModule for native Android foreground service binding
- Refactor backgroundService to integrate foreground service and expo-background-task

Also refactor auth and profile screens to use dynamic theme colors:
- Replace hardcoded THEME_COLORS with colors.primary.main, colors.background.paper, etc.
- Add useResolvedColorScheme for dynamic StatusBar styling
- Update NotificationSettingsScreen with sync mode selection UI

BREAKING CHANGE: Switched from expo-background-fetch to expo-background-task, minimum background sync interval changed from 900s to 15min in config

package.json

@@ -1,6 +1,6 @@
 {
   "name": "carrot_bbs",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "main": "expo-router/entry",
   "scripts": {
     "start": "expo start",
@@ -25,7 +25,6 @@
     "axios": "^1.13.6",
     "date-fns": "^4.1.0",
     "expo": "~55.0.4",
-    "expo-background-fetch": "~55.0.10",
     "expo-background-task": "~55.0.10",
     "expo-camera": "^55.0.10",
     "expo-constants": "~55.0.7",