- Add `/youtube/transcript` POST endpoint to Swagger docs
- Define `YouTubeRequest` schema with URL, language, timestamps fields
- Define `YouTubeResponse` schema with transcript and metadata fields
- Add API security requirement using ApiKeyAuth
- Document 200, 400, and 500 response codes
- Add godoc comments to YouTubeHandler struct methods
- Include example values for all request/response properties
### CHANGES
- Introduce `cmd` directory for all main application binaries.
- Move all Go packages into the `internal` directory.
- Rename the `restapi` package to `server` for clarity.
- Consolidate patterns and strategies into a new `data` directory.
- Group all auxiliary scripts into a new `scripts` directory.
- Move all documentation and images into a `docs` directory.
- Update all Go import paths to reflect the new structure.
- Adjust CI/CD workflows and build commands for new layout.