feat(post): enhance post handling with channel integration

- Updated PostHandler to include channel information in post responses.
- Introduced PostChannelBrief DTO to represent channel details associated with posts.
- Modified post conversion functions to support channel data, ensuring proper mapping of channel IDs to channel names.
- Enhanced ChannelRepository and ChannelService to facilitate batch retrieval of channels by IDs.
- Updated wire generation to inject channel service into post handler for improved functionality.

internal/dto/dto.go

@@ -120,6 +120,12 @@ type AdminUpdateUserStatusRequest struct {
 
 // ==================== Post DTOs ====================
 
+// PostChannelBrief 帖子所属频道（列表/详情卡片展示）
+type PostChannelBrief struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+}
+
 // PostImageResponse 帖子图片响应
 type PostImageResponse struct {
 	ID              string `json:"id"`
@@ -154,6 +160,7 @@ type PostResponse struct {
 	Author         *UserResponse       `json:"author"`
 	IsLiked        bool                `json:"is_liked"`
 	IsFavorited    bool                `json:"is_favorited"`
+	Channel        *PostChannelBrief   `json:"channel,omitempty"`
 }
 
 // PostDetailResponse 帖子详情响应
@@ -179,6 +186,7 @@ type PostDetailResponse struct {
 	Author         *UserResponse       `json:"author"`
 	IsLiked        bool                `json:"is_liked"`
 	IsFavorited    bool                `json:"is_favorited"`
+	Channel        *PostChannelBrief   `json:"channel,omitempty"`
 }
 
 // ==================== Comment DTOs ====================