refactor(model-type): complete phase 5 cleanup by removing deprecated model_type field

- Remove backward compatibility code for `model_type` in `ModelScanner._build_cache_entry()`
- Update `CheckpointScanner` to only handle `sub_type` in `adjust_metadata()` and `adjust_cached_entry()`
- Delete deprecated aliases `resolve_civitai_model_type` and `normalize_civitai_model_type` from `model_query.py`
- Update frontend components (`RecipeModal.js`, `ModelCard.js`, etc.) to use `sub_type` instead of `model_type`
- Update API response format to return only `sub_type`, removing `model_type` from service responses
- Revise technical documentation to mark Phase 5 as completed and remove outdated TODO items

All cleanup tasks for the model type refactoring are now complete, ensuring consistent use of `sub_type` across the codebase.

py/services/checkpoint_service.py

@@ -22,8 +22,8 @@ class CheckpointService(BaseModelService):
     
     async def format_response(self, checkpoint_data: Dict) -> Dict:
         """Format Checkpoint data for API response"""
-        # Get sub_type from cache entry (new field) or fallback to model_type (old field)
-        sub_type = checkpoint_data.get("sub_type") or checkpoint_data.get("model_type", "checkpoint")
+        # Get sub_type from cache entry (new canonical field)
+        sub_type = checkpoint_data.get("sub_type", "checkpoint")
         
         return {
             "model_name": checkpoint_data["model_name"],
@@ -40,8 +40,7 @@ class CheckpointService(BaseModelService):
             "from_civitai": checkpoint_data.get("from_civitai", True),
             "usage_count": checkpoint_data.get("usage_count", 0),
             "notes": checkpoint_data.get("notes", ""),
-            "sub_type": sub_type,  # New canonical field
-            "model_type": sub_type,  # Backward compatibility
+            "sub_type": sub_type,
             "favorite": checkpoint_data.get("favorite", False),
             "update_available": bool(checkpoint_data.get("update_available", False)),
             "civitai": self.filter_civitai_data(checkpoint_data.get("civitai", {}), minimal=True)