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/message/GroupInfoScreen.tsx

@@ -49,8 +49,8 @@ import { User } from '../../types';
 import { blurActiveElement } from '../../infrastructure/platform';
 import { firstRouteParam } from '../../navigation/paramUtils';
 import * as hrefs from '../../navigation/hrefs';
-import { messageManager } from '../../stores/messageManager';
-import { groupManager } from '../../stores/groupManager';
+import { messageManager } from '../../stores/message';
+import { groupManager } from '../../stores/group';
 import MutualFollowSelectorModal from './components/MutualFollowSelectorModal';
 import { AppBackButton } from '../../components/common';