fix(download): accept newer CivitAI file types for primary file selection

Downloads failed with "No suitable file found in metadata" for models whose
only file uses newer CivitAI file types (e.g. 'Enhancement LoRA' for
Anima/AIR image-editing LoRAs) because the primary-file allowlist only
covered legacy types.

- unify the weights-type allowlist as MODEL_WEIGHT_FILE_TYPES
  (py/utils/constants.py) and apply it across download, recipe and
  metadata-refresh lookups
- mirror CivitAI's getPrimaryFile() semantics: prefer weights-type primary,
  fall back to weights files, then trust CivitAI's primary flag (excluding
  non-downloadable artifacts like Config/Archive/Workflow)
- mirror the allowlist in the frontend via shared isModelWeightFile() helper
- add regression tests for the Enhancement LoRA primary-file download,
  primary-flag fallback and weights-over-non-weights-primary preference

py/routes/base_model_routes.py

@@ -30,6 +30,7 @@ from ..services.websocket_progress_callback import (
     WebSocketProgressCallback,
 )
 from ..utils.exif_utils import ExifUtils
+from ..utils.constants import MODEL_WEIGHT_FILE_TYPES
 from ..utils.metadata_manager import MetadataManager
 from .model_route_registrar import COMMON_ROUTE_DEFINITIONS, ModelRouteRegistrar
 from .handlers.model_handlers import (
@@ -251,7 +252,7 @@ class BaseModelRoutes(ABC):
 
     def _find_model_file(self, files):
         """Find the appropriate model file from the files list - can be overridden by subclasses."""
-        return next((file for file in files if file.get("type") in ("Model", "Diffusion Model") and file.get("primary") is True), None)
+        return next((file for file in files if file.get("type") in MODEL_WEIGHT_FILE_TYPES and file.get("primary") is True), None)
 
     def get_handler(self, name: str) -> Callable[[web.Request], Awaitable[web.StreamResponse]]:
         """Expose handlers for subclasses or tests."""