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/router/router.go

@@ -23,6 +23,7 @@ type Router struct {
 	groupHandler          *handler.GroupHandler
 	stickerHandler        *handler.StickerHandler
 	voteHandler           *handler.VoteHandler
+	channelHandler        *handler.ChannelHandler
 	scheduleHandler       *handler.ScheduleHandler
 	roleHandler           *handler.RoleHandler
 	adminUserHandler      *handler.AdminUserHandler
@@ -51,6 +52,7 @@ func New(
 	groupHandler *handler.GroupHandler,
 	stickerHandler *handler.StickerHandler,
 	voteHandler *handler.VoteHandler,
+	channelHandler *handler.ChannelHandler,
 	scheduleHandler *handler.ScheduleHandler,
 	roleHandler *handler.RoleHandler,
 	adminUserHandler *handler.AdminUserHandler,
@@ -82,6 +84,7 @@ func New(
 		groupHandler:          groupHandler,
 		stickerHandler:        stickerHandler,
 		voteHandler:           voteHandler,
+		channelHandler:        channelHandler,
 		scheduleHandler:       scheduleHandler,
 		roleHandler:           roleHandler,
 		adminUserHandler:      adminUserHandler,
@@ -238,6 +241,14 @@ func (r *Router) setupRoutes() {
 			posts.DELETE("/:id/vote", authMiddleware, r.voteHandler.Unvote)                            // 取消投票
 		}
 
+		// 频道路由（公开）
+		if r.channelHandler != nil {
+			channels := v1.Group("/channels")
+			{
+				channels.GET("", r.channelHandler.ListPublic)
+			}
+		}
+
 		// 课表路由
 		if r.scheduleHandler != nil {
 			schedule := v1.Group("/schedule")
@@ -449,6 +460,14 @@ func (r *Router) setupRoutes() {
 					admin.PUT("/posts/:id/feature", r.adminPostHandler.SetPostFeature)
 				}
 
+				// 频道管理
+				if r.channelHandler != nil {
+					admin.GET("/channels", r.channelHandler.AdminList)
+					admin.POST("/channels", r.channelHandler.AdminCreate)
+					admin.PUT("/channels/:id", r.channelHandler.AdminUpdate)
+					admin.DELETE("/channels/:id", r.channelHandler.AdminDelete)
+				}
+
 				// 评论管理
 				if r.adminCommentHandler != nil {
 					admin.GET("/comments", r.adminCommentHandler.GetCommentList)