- GET /tags returns deduplicated sorted array of all tags across todos
- POST /todos/:id/tags attaches a tag to a todo (idempotent, ignores duplicates)
- DELETE /todos/:id/tags/:tag removes a specific tag from a todo
- Both /todos/:id/tags routes return 404 for non-existent todos
- Add tags:[] to all seed todo objects
- POST /todos accepts optional tags array (defaults to [])
- GET /todos?tag=<value> filters to todos whose tags include that value (case-sensitive)
Closes#14