The Go module name has been changed from `carrot_bbs` to `with_you`, which requires
all import paths to be updated throughout the codebase and by external consumers.
BREAKING CHANGE: Module name changed from carrot_bbs to with_you. All imports
and dependencies must be updated from carrot_bbs/* to with_you/*.
- 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.
