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/services/postService.ts

@@ -29,6 +29,7 @@ interface CreatePostRequest {
   title: string;
   content: string;
   images?: string[];
+  channel_id?: string;
 }
 
 // 更新帖子请求
@@ -45,7 +46,7 @@ class PostService {
     page = 1,
     pageSize = 20,
     tab?: string,
-    communityId?: string
+    channelId?: string
   ): Promise<PaginatedData<Post>> {
     const params: Record<string, any> = {
       page,
@@ -55,8 +56,8 @@ class PostService {
     if (tab) {
       params.tab = tab;
     }
-    if (communityId) {
-      params.community_id = communityId;
+    if (channelId) {
+      params.channel_id = channelId;
     }
     
     const response = await api.get<PostListResponse>('/posts', params);