This PR refactors the movie and tv modules and adds a "common" module
for shared logic.
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## Summary by CodeRabbit
* **New Features**
* Dedicated import and metadata services for movies and TV;
completed-torrent detection and import flows.
* **Refactor**
* Shared media schemas, models, repository logic and base services
consolidated; movie/TV services and routes now delegate to specialised
import/metadata services.
* **Bug Fixes**
* Fixed TV episode-count method name.
* **Chores**
* Added .DS_Store to ignore list; added module comment.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
