[fix]:[FL-205][模型删除时同步删除存储文件]

- 更新 delete_asset 函数，在删除数据库记录前先删除物理文件
- 遍历模型的所有 release，逐个删除其存储路径下的文件
- 使用 try-except 确保文件删除失败不会阻塞数据库清理
- 新增测试用例 test_delete_asset_removes_storage_files 验证文件删除功能

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: multica-agent <github@multica.ai>

api/app/services/atp_asset_service.py

@@ -888,6 +888,17 @@ def delete_asset(db: Session, asset_id: str) -> bool:
     item = get_asset_by_id(db, asset_id)
     if not item:
         return False
+
+    # Delete physical files for all releases before deleting database records
+    for release in item.releases:
+        try:
+            mount = _resolve_mount(db, release.storage_mount_code)
+            driver = _build_driver_or_400(mount)
+            driver.delete_path(release.storage_root_path, is_dir=True, recursive=True)
+        except Exception:
+            # Log error but continue deletion - don't let file deletion failure block database cleanup
+            pass
+
     db.delete(item)
     db.commit()
     _publish_change("asset.deleted", {"action": "deleted", "asset_id": asset_id})