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.

cmd/server/wire.go

@@ -36,6 +36,7 @@ func ProvideRouter(
 	groupHandler *handler.GroupHandler,
 	stickerHandler *handler.StickerHandler,
 	voteHandler *handler.VoteHandler,
+	channelHandler *handler.ChannelHandler,
 	scheduleHandler *handler.ScheduleHandler,
 	roleHandler *handler.RoleHandler,
 	adminUserHandler *handler.AdminUserHandler,
@@ -62,6 +63,7 @@ func ProvideRouter(
 		groupHandler,
 		stickerHandler,
 		voteHandler,
+		channelHandler,
 		scheduleHandler,
 		roleHandler,
 		adminUserHandler,