refactor: 架构重构 - 解耦过度耦合模块

主要改动:
1. 创建乐观更新工具函数 (optimisticUpdate.ts)
   - 消除 userStore.ts 中的重复代码

2. 拆分 useResponsive.ts (485行 -> 12个专注模块)
   - useBreakpoint: 断点检测
   - useOrientation: 方向检测
   - usePlatform: 平台检测
   - useScreenSize: 屏幕尺寸
   - useResponsiveValue: 响应式值
   - useResponsiveStyle: 响应式样式
   - useMediaQuery: 媒体查询
   - useColumnCount: 列数计算
   - useResponsiveSpacing: 响应式间距

3. 整理数据层 (Repository 层)
   - ApiDataSource: API数据源
   - LocalDataSource: 本地数据源
   - CacheDataSource: 缓存数据源
   - MessageRepository: 消息仓库

4. 重构 messageManager.ts (2194行 -> 4个模块)
   - MessageStateManager: 状态管理
   - WebSocketMessageHandler: WebSocket处理
   - MessageSyncService: 消息同步
   - ReadReceiptManager: 已读管理

5. 导航解耦 (MainNavigator.tsx: 1118行 -> 100行)
   - 创建 NavigationService 解耦层
   - 拆分多个 Navigator 组件

架构改进:
- 单一职责原则: 每个模块职责明确
- 依赖倒置: 通过接口解耦
- 代码复用: 工具函数可被多处使用
- 可测试性: 各模块可独立测试

src/data/mappers/UserMapper.ts

@@ -0,0 +1,168 @@
+/**
+ * 用户数据映射器
+ * 负责 User 模型与 API 响应、数据库记录之间的转换
+ */
+
+import { UserModel } from '../models';
+import type { UserDTO, User } from '../../types/dto';
+
+// 数据库用户记录类型
+export interface UserDbRecord {
+  id: string;
+  data: string;
+  updatedAt: string;
+}
+
+export class UserMapper {
+  /**
+   * 将 API DTO 转换为应用模型
+   */
+  static fromDTO(dto: UserDTO): UserModel {
+    return {
+      id: String(dto.id || ''),
+      username: dto.username || '',
+      nickname: dto.nickname,
+      avatar: dto.avatar,
+      bio: dto.bio,
+      website: dto.website,
+      location: dto.location,
+      email: dto.email,
+      phone: dto.phone,
+      followersCount: dto.followers_count,
+      followingCount: dto.following_count,
+      postsCount: dto.posts_count,
+      isFollowing: dto.is_following,
+      isBlocked: dto.is_blocked,
+      createdAt: dto.created_at ? new Date(dto.created_at) : undefined,
+      updatedAt: dto.updated_at ? new Date(dto.updated_at) : undefined,
+    };
+  }
+
+  /**
+   * 将 User 类型转换为应用模型
+   */
+  static fromUser(user: User): UserModel {
+    return {
+      id: String(user.id || ''),
+      username: user.username || '',
+      nickname: user.nickname,
+      avatar: user.avatar,
+      bio: user.bio,
+      website: user.website,
+      location: user.location,
+      email: user.email,
+      phone: user.phone,
+      followersCount: user.followers_count,
+      followingCount: user.following_count,
+      postsCount: user.posts_count,
+      isFollowing: user.is_following,
+      isBlocked: user.is_blocked,
+      createdAt: user.created_at ? new Date(user.created_at) : undefined,
+      updatedAt: user.updated_at ? new Date(user.updated_at) : undefined,
+    };
+  }
+
+  /**
+   * 将 DTO 数组转换为应用模型数组
+   */
+  static fromDTOList(dtos: UserDTO[]): UserModel[] {
+    return dtos.map(dto => this.fromDTO(dto));
+  }
+
+  /**
+   * 从数据库记录转换为应用模型
+   */
+  static fromDbRecord(record: UserDbRecord): UserModel | null {
+    try {
+      const data = JSON.parse(record.data) as UserDTO;
+      return this.fromDTO(data);
+    } catch {
+      return null;
+    }
+  }
+
+  /**
+   * 将应用模型转换为数据库记录
+   */
+  static toDbRecord(model: UserModel): UserDbRecord {
+    const dto: UserDTO = {
+      id: model.id,
+      username: model.username,
+      nickname: model.nickname,
+      avatar: model.avatar,
+      bio: model.bio,
+      website: model.website,
+      location: model.location,
+      email: model.email,
+      phone: model.phone,
+      followers_count: model.followersCount,
+      following_count: model.followingCount,
+      posts_count: model.postsCount,
+      is_following: model.isFollowing,
+      is_blocked: model.isBlocked,
+      created_at: model.createdAt?.toISOString(),
+      updated_at: model.updatedAt?.toISOString(),
+    };
+
+    return {
+      id: model.id,
+      data: JSON.stringify(dto),
+      updatedAt: new Date().toISOString(),
+    };
+  }
+
+  /**
+   * 将应用模型转换为 API 请求数据
+   */
+  static toApiRequest(model: Partial<UserModel>): Record<string, any> {
+    const request: Record<string, any> = {};
+
+    if (model.nickname !== undefined) {
+      request.nickname = model.nickname;
+    }
+    if (model.avatar !== undefined) {
+      request.avatar = model.avatar;
+    }
+    if (model.bio !== undefined) {
+      request.bio = model.bio;
+    }
+    if (model.website !== undefined) {
+      request.website = model.website;
+    }
+    if (model.location !== undefined) {
+      request.location = model.location;
+    }
+    if (model.phone !== undefined) {
+      request.phone = model.phone;
+    }
+    if (model.email !== undefined) {
+      request.email = model.email;
+    }
+
+    return request;
+  }
+
+  /**
+   * 将应用模型转换为 DTO
+   */
+  static toDTO(model: UserModel): UserDTO {
+    return {
+      id: model.id,
+      username: model.username,
+      nickname: model.nickname,
+      avatar: model.avatar,
+      bio: model.bio,
+      website: model.website,
+      location: model.location,
+      email: model.email,
+      phone: model.phone,
+      followers_count: model.followersCount,
+      following_count: model.followingCount,
+      posts_count: model.postsCount,
+      is_following: model.isFollowing,
+      is_blocked: model.isBlocked,
+      created_at: model.createdAt?.toISOString(),
+      updated_at: model.updatedAt?.toISOString(),
+    };
+  }
+}