feat(pagination): implement cursor-based pagination across the app

Add useCursorPagination hook and update multiple screens and services
to use cursor-based pagination for better performance and consistency.

- Add useCursorPagination hook with deduplication and caching support
- Add cursor pagination types to infrastructure layer
- Refactor HomeScreen, PostDetailScreen, SearchScreen for posts/comments
- Refactor GroupMembersScreen, JoinGroupScreen for groups/members
- Refactor MessageListScreen, NotificationsScreen for messages
- Update post, message, group, comment, notification services with cursor endpoints
- Add CursorPaginationRequest/Response DTOs
- Remove deprecated OPTIMIZATION_DESIGN.md documentation

src/types/dto.ts

@@ -499,6 +499,36 @@ export interface SystemUnreadCountResponse {
 // 设备类型
 export type DeviceType = 'ios' | 'android' | 'web';
 
+// ==================== 游标分页相关 DTO ====================
+
+/**
+ * 游标分页请求参数
+ */
+export interface CursorPaginationRequest {
+  /** 游标字符串（可选，首次请求不传） */
+  cursor?: string;
+  /** 分页方向：forward 或 backward（默认 forward） */
+  direction?: 'forward' | 'backward';
+  /** 每页数量（默认 20，最大 100） */
+  page_size?: number;
+  /** 帖子类型筛选（可选）：recommend, follow, hot, latest */
+  post_type?: 'recommend' | 'follow' | 'hot' | 'latest';
+}
+
+/**
+ * 游标分页响应
+ */
+export interface CursorPaginationResponse<T> {
+  /** 数据项列表 */
+  items: T[];
+  /** 下一页游标 */
+  next_cursor: string | null;
+  /** 上一页游标 */
+  prev_cursor: string | null;
+  /** 是否有更多数据 */
+  has_more: boolean;
+}
+
 // 设备Token响应
 export interface DeviceTokenResponse {
   id: number;