feat: dSYM 按上传配置一并保存到远端，本地清理后回退到远端地址下载

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_downloads.py

@@ -66,6 +66,18 @@ def test_download_dsym_nonexistent_task(client, tmp_config):
     assert resp.status_code == 404
 
 
+def test_download_dsym_remote_fallback(client, tmp_config):
+    """本地文件已被清理，但保存了远端地址时应重定向到远端"""
+    task_id = _create_task_with_files(
+        client, tmp_config,
+        dsym_path="/tmp/nonexistent.dSYM",
+        dsym_url="https://oss.example.com/ios-builds/iOS/app_1_0_0_main_adhoc.dSYM.zip",
+    )
+    resp = client.get(f"/api/tasks/{task_id}/dsym", follow_redirects=False)
+    assert resp.status_code in (302, 307)
+    assert resp.headers["location"] == "https://oss.example.com/ios-builds/iOS/app_1_0_0_main_adhoc.dSYM.zip"
+
+
 # ---- 混淆映射表下载 ----
 
 def test_download_obfuscation_maps_not_exist(client, tmp_config):