refactor(database): migrate to new modular database layer and unify data access

- Remove legacy database.ts, LocalDataSource.ts, and MessageRepository.ts
- Create new src/database/ module with messageRepository, userCacheRepository, conversationRepository, and groupCacheRepository
- Update all consumers to import from @/database instead of services/database
- Add web platform blur handling for modal components to fix focus issues
- Flatten SystemMessageItem and NotificationsScreen styles for consistent design
- Add draggable slider in ChatSettingsScreen and dynamic font size support
- Introduce 9 new chat color themes
- Add profile screens for about, terms, and privacy policy with navigation routes
- Add policy links to login and registration screens
- Fix post share URL format from /posts/ to /post/

src/navigation/hrefs.ts

@@ -177,3 +177,17 @@ export function hrefMaterialSubject(subjectId: string): string {
 export function hrefMaterialDetail(materialId: string): string {
   return `/apps/materials/detail?materialId=${encodeURIComponent(materialId)}`;
 }
+
+// ==================== Profile Settings (设置相关) ====================
+
+export function hrefProfileAbout(): string {
+  return '/profile/about';
+}
+
+export function hrefProfileTerms(): string {
+  return '/profile/terms';
+}
+
+export function hrefProfilePrivacy(): string {
+  return '/profile/privacy';
+}