refactor(Post, PostMapper, PostRepository, CreatePostScreen, HomeScreen): update communityId to channelId for improved clarity

- Renamed communityId to channelId across Post entity, PostMapper, and PostRepository for consistency and clarity.
- Updated CreatePostScreen to include channel selection functionality, enhancing user experience when creating posts.
- Adjusted HomeScreen to support filtering posts by channel, improving content organization.
- Refactored related interfaces and services to align with the new channelId terminology, ensuring a cohesive codebase.

src/core/entities/Post.ts

@@ -75,8 +75,8 @@ export interface Post {
   isPinned: boolean;
   /** 帖子状态 */
   status: PostStatus;
-  /** 所属社区ID */
-  communityId?: string;
+  /** 所属频道ID */
+  channelId?: string;
   /** 标签列表 */
   tags: string[];
   /** 创建时间 */
@@ -113,8 +113,8 @@ export interface Post {
   updated_at?: string;
   /** @deprecated 请使用 contentEditedAt */
   content_edited_at?: string;
-  /** @deprecated 请使用 communityId */
-  community_id?: string;
+  /** @deprecated 请使用 channelId */
+  channel_id?: string;
   /** @deprecated 请使用 status */
   status_str?: string;
   /** 投票帖子标识 (部分旧代码使用) */
@@ -168,7 +168,7 @@ export const createPost = (data: Partial<Post>): Post => ({
   isFavorited: data.isFavorited || false,
   isPinned: data.isPinned || false,
   status: data.status || 'published',
-  communityId: data.communityId,
+  channelId: data.channelId,
   tags: data.tags || [],
   createdAt: data.createdAt || new Date().toISOString(),
   updatedAt: data.updatedAt || new Date().toISOString(),