- Add Offline status to ModelStatus enum
- Sync marks all models offline first, then activates found ones
- Deduplicate by model name (ignoring provider)
- Deactivate orphaned models (offline -> deprecated)
- Add models_offline and models_deactivated to SyncModelsResponse
- Add deduplicate_existing_models() for cleanup
- Rename upsert_model to upsert_model_by_name