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

src/components/business/SystemMessageItem.tsx

@@ -125,12 +125,12 @@ function createSystemMessageStyles(colors: AppColors) {
       flexDirection: 'row',
       alignItems: 'flex-start',
       padding: 16,
-      backgroundColor: '#fff',
+      backgroundColor: colors.background.paper,
       borderBottomWidth: 1,
       borderBottomColor: colors.divider || '#E5E5EA',
     },
     unreadContainer: {
-      backgroundColor: '#FFF8F6',
+      backgroundColor: colors.primary.main + '0A',
     },
     unreadIndicator: {
       position: 'absolute',
@@ -140,7 +140,7 @@ function createSystemMessageStyles(colors: AppColors) {
       width: 8,
       height: 8,
       borderRadius: 4,
-      backgroundColor: '#FF6B35',
+      backgroundColor: colors.primary.main,
     },
     iconContainer: {
       marginRight: 14,
@@ -165,7 +165,7 @@ function createSystemMessageStyles(colors: AppColors) {
       justifyContent: 'center',
       alignItems: 'center',
       borderWidth: 2,
-      borderColor: '#fff',
+      borderColor: colors.background.paper,
     },
     content: {
       flex: 1,
@@ -220,7 +220,7 @@ function createSystemMessageStyles(colors: AppColors) {
       flexDirection: 'row',
       alignItems: 'center',
       marginTop: 8,
-      backgroundColor: '#F5F5F7',
+      backgroundColor: colors.background.default,
       paddingHorizontal: 10,
       paddingVertical: 6,
       borderRadius: 8,
@@ -318,13 +318,6 @@ const getSystemMessageTitle = (message: SystemMessageResponse): string => {
   }
 };
 
-// 胡萝卜橙主题色
-const THEME_COLORS = {
-  primary: '#FF6B35',
-  primaryLight: '#FF8C5A',
-  primaryDark: '#E55A2B',
-};
-
 const SystemMessageItem: React.FC<SystemMessageItemProps> = ({
   message,
   onPress,