feat: layout hamburger, media browser filters+previews, billing fixes

- Layout: mobile hamburger menu + overlay backdrop + close button; content area always full-width
- Media browser: filter chips (default still+turntable); advanced toggle for GLB/STL; thumbnail_url previews for non-image types; video hover-play for turntable
- Backend: asset_types multi-filter, thumbnail_url in MediaAssetOut, download proxy endpoint for MinIO/local files
- Admin: "Import Existing Media" button → POST /api/admin/import-media-assets
- Billing: fix invoice create 500 (MissingGreenlet — use selectinload after commit); PDF download uses axios blob instead of bare <a href> (auth header missing); fix storage.upload() accepting str|Path
- SSE task logs: task_logs.py core + router, LiveRenderLog component
- CadPreview: fix infinite loop when no gltf_geometry assets; loading screen before ThreeDViewer render
- render-worker: add trimesh layer to Dockerfile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/core/storage.py

@@ -56,8 +56,9 @@ class MinIOStorage:
             except Exception as exc:
                 logger.warning("Could not create MinIO bucket %s: %s", self._bucket, exc)
 
-    def upload(self, local_path: Path, object_key: str) -> str:
+    def upload(self, local_path: Path | str, object_key: str) -> str:
         """Upload a local file to MinIO. Returns the object_key."""
+        local_path = Path(local_path)
         self._client.upload_file(str(local_path), self._bucket, object_key)
         logger.debug("Uploaded %s → minio://%s/%s", local_path.name, self._bucket, object_key)
         return object_key