refactor(stores): reorganize flat store files into modular directory structure

Migrate from flat file organization to modular directory structure under src/stores/:

- auth/: authStore, registerStore, verificationStore, sessionStore
- call/: callStore
- settings/: chatSettingsStore, themeStore
- ui/: homeTabBarVisibilityStore, homeTabPressStore
- utils/: routePayloadCache
- group/sources.ts, group/profileResolver.ts
- message/sources.ts
- post/sources.ts

Update all import paths across components and screens to use new module paths. Maintain backward compatibility through deprecated re-export files for gradual migration.

src/screens/profile/ChatSettingsScreen.tsx

@@ -26,7 +26,7 @@ import {
   useChatSettingsStore,
   useChatSettingsActions,
   CHAT_THEMES,
-} from '../../stores/chatSettingsStore';
+} from '../../stores/settings';
 
 const { width: SCREEN_WIDTH } = Dimensions.get('window');
 const CARD_MAX_WIDTH = 720;

src/screens/profile/UserScreen.tsx

@@ -7,7 +7,7 @@
 import React from 'react';
 import { useLocalSearchParams } from 'expo-router';
 import UserProfileScreen from './UserProfileScreen';
-import { useCurrentUser } from '../../stores/authStore';
+import { useCurrentUser } from '../../stores/auth';
 
 export const UserScreen: React.FC = () => {
   const { userId: userIdParam } = useLocalSearchParams<{ userId?: string }>();

src/screens/profile/VerificationSettingsScreen.tsx

@@ -22,7 +22,7 @@ import {
   useVerificationStore,
   useVerificationStatus,
   useVerificationLoading,
-} from '../../stores/verificationStore';
+} from '../../stores/auth';
 import { showPrompt } from '@/services/ui';
 import * as hrefs from '../../navigation/hrefs';
 

src/screens/profile/useUserProfile.ts

@@ -10,10 +10,10 @@ import { useSafeAreaInsets } from 'react-native-safe-area-context';
 import { spacing, type AppColors } from '../../theme';
 import { Post, User } from '../../types';
 import { useUserStore } from '../../stores';
-import { useCurrentUser } from '../../stores/authStore';
+import { useCurrentUser } from '../../stores/auth';
 import { postService, authService, messageService } from '../../services';
 import { postSyncService } from '@/services/post';
-import { userManager } from '../../stores/userManager';
+import { userManager } from '../../stores/user';
 import * as hrefs from '../../navigation/hrefs';
 import { PostCardAction } from '../../components/business/PostCard';