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/types/dto.ts

@@ -80,7 +80,7 @@ export interface PostDTO {
   is_liked: boolean;
   is_favorited: boolean;
   // 额外字段
-  community_id?: string;
+  channel_id?: string;
   top_comment?: CommentDTO | null;
 }
 
@@ -780,7 +780,7 @@ export interface VoteResultDTO {
 export interface CreateVotePostRequest {
   title: string;
   content?: string;
-  community_id?: string;
+  channel_id?: string;
   images?: string[];
   vote_options: string[]; // 至少2个，最多10个
 }

src/types/index.ts

@@ -102,6 +102,7 @@ export interface CreatePostInput {
   title: string;
   content: string;
   images?: string[]; // 本地图片路径或 base64
+  channel_id?: string;
 }
 
 // ============================================