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- Revise technical documentation to mark Phase 5 as completed and remove outdated TODO items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.

tests/services/test_model_scanner.py

@@ -521,7 +521,7 @@ async def test_reconcile_cache_applies_adjust_cached_entry(tmp_path: Path):
 
     def _adjust(self, entry: dict) -> dict:
         applied.append(entry["file_path"])
-        entry["model_type"] = "adjusted"
+        entry["custom_field"] = "adjusted"
         return entry
 
     scanner.adjust_cached_entry = MethodType(_adjust, scanner)
@@ -538,7 +538,7 @@ async def test_reconcile_cache_applies_adjust_cached_entry(tmp_path: Path):
     assert normalized_new in applied
 
     new_entry = next(item for item in scanner._cache.raw_data if item["file_path"] == normalized_new)
-    assert new_entry["model_type"] == "adjusted"
+    assert new_entry["custom_field"] == "adjusted"
 
 
 @pytest.mark.asyncio