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/screens/profile/AccountDeletionScreen.tsx

@@ -21,13 +21,6 @@ import * as hrefs from '../../navigation/hrefs';
 
 const CONTENT_MAX_WIDTH = 720;
 
-// 胡萝卜橙主题色
-const THEME_COLORS = {
-  primary: '#FF6B35',
-  primaryLight: '#FF8C5A',
-  primaryDark: '#E55A2B',
-};
-
 function createAccountDeletionStyles(colors: AppColors) {
   return StyleSheet.create({
     container: {
@@ -114,7 +107,7 @@ function createAccountDeletionStyles(colors: AppColors) {
     },
     // 输入框 - 扁平化风格
     input: {
-      backgroundColor: '#F5F5F7',
+      backgroundColor: colors.background.default,
       borderRadius: 14,
       padding: spacing.md,
       fontSize: 16,
@@ -133,12 +126,12 @@ function createAccountDeletionStyles(colors: AppColors) {
       flex: 1,
       height: 56,
       borderRadius: 14,
-      backgroundColor: THEME_COLORS.primary,
+      backgroundColor: colors.primary.main,
       alignItems: 'center',
       justifyContent: 'center',
     },
     primaryButtonText: {
-      color: '#fff',
+      color: colors.text.inverse,
       fontSize: fontSizes.md,
       fontWeight: '600',
     },
@@ -166,7 +159,7 @@ function createAccountDeletionStyles(colors: AppColors) {
       justifyContent: 'center',
     },
     dangerButtonText: {
-      color: '#fff',
+      color: colors.text.inverse,
       fontSize: fontSizes.md,
       fontWeight: '600',
     },
@@ -392,9 +385,9 @@ export const AccountDeletionScreen: React.FC = () => {
                   onPress={handleRequestDeletion}
                   disabled={submitting || !password.trim()}
                 >
-                  {submitting ? (
-                    <ActivityIndicator size="small" color="#fff" />
-                  ) : (
+              {submitting ? (
+                <ActivityIndicator size="small" color={colors.text.inverse} />
+              ) : (
                     <Text style={styles.dangerButtonText}>确认注销</Text>
                   )}
                 </TouchableOpacity>