修复下载模型问题

backend/app/services/model_service.py

@@ -1,3 +1,4 @@
+import os
 import json
 from pathlib import Path
 from typing import Any
@@ -42,13 +43,16 @@ async def download_model(model_id: str, use_modelscope: bool = False) -> dict[st
     """从 HF 或 ModelScope 下载模型到本地缓存。"""
     try:
         if use_modelscope:
-            from modelscope.hub.snapshot_download import snapshot_download as ms_snapshot_download
+            import subprocess
 
             download_dir = str(settings.models_dir / model_id.replace("/", "_"))
-            local_path = ms_snapshot_download(
-                model_id,
-                local_dir=download_dir,
+            proc = subprocess.run(
+                ["modelscope", "download", "--model", model_id, "--local_dir", download_dir],
+                capture_output=True, text=True, timeout=3600,
             )
+            if proc.returncode != 0:
+                raise RuntimeError(f"modelscope CLI failed: {proc.stderr}")
+            local_path = download_dir
         else:
             from huggingface_hub import snapshot_download