feat(channel): integrate channel functionality into post management

- Added Channel support in Post model, including ChannelID field in PostRequest and PostResponse DTOs.
- Updated PostService and PostRepository to handle channel-specific logic for creating and listing posts.
- Introduced ChannelRepository and ChannelService, along with corresponding handlers for managing channels.
- Enhanced router to include routes for channel management and public channel listing.
- Seeded default channels in the database during initialization.

internal/service/vote_service.go

@@ -52,12 +52,12 @@ func (s *VoteService) CreateVotePost(ctx context.Context, userID string, req *dt
 
 	// 创建普通帖子（设置IsVote=true）
 	post := &model.Post{
-		UserID:      userID,
-		CommunityID: req.CommunityID,
-		Title:       req.Title,
-		Content:     req.Content,
-		Status:      model.PostStatusPending,
-		IsVote:      true,
+		UserID:    userID,
+		ChannelID: req.ChannelID,
+		Title:     req.Title,
+		Content:   req.Content,
+		Status:    model.PostStatusPending,
+		IsVote:    true,
 	}
 
 	err := s.postRepo.Create(post, req.Images)