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/database/repositories/PostCacheRepository.ts

@@ -0,0 +1,44 @@
+import { localDataSource } from '../LocalDataSource';
+import type { ILocalDataSource } from '@/data/datasources/interfaces';
+
+export interface IPostCacheRepository {
+  save(id: string, data: any): Promise<void>;
+  get(id: string): Promise<any | null>;
+  getAll(): Promise<any[]>;
+  delete(id: string): Promise<void>;
+}
+
+export class PostCacheRepository implements IPostCacheRepository {
+  constructor(private dataSource: ILocalDataSource = localDataSource) {}
+
+  async save(id: string, data: any): Promise<void> {
+    await this.dataSource.enqueueWrite(async () => {
+      await this.dataSource.run(
+        `INSERT OR REPLACE INTO posts_cache (id, data, updatedAt) VALUES (?, ?, ?)`,
+        [String(id), JSON.stringify(data), new Date().toISOString()]
+      );
+    });
+  }
+
+  async get(id: string): Promise<any | null> {
+    const r = await this.dataSource.getFirst<{ data: string }>(
+      `SELECT data FROM posts_cache WHERE id = ?`, [String(id)]
+    );
+    return r?.data ? JSON.parse(r.data) : null;
+  }
+
+  async getAll(): Promise<any[]> {
+    const rows = await this.dataSource.query<{ data: string }>(
+      `SELECT data FROM posts_cache ORDER BY updatedAt DESC`
+    );
+    return rows.map(r => JSON.parse(r.data));
+  }
+
+  async delete(id: string): Promise<void> {
+    await this.dataSource.enqueueWrite(async () => {
+      await this.dataSource.run(`DELETE FROM posts_cache WHERE id = ?`, [String(id)]);
+    });
+  }
+}
+
+export const postCacheRepository = new PostCacheRepository();