fix: clarify New-API authentication failures

backend/test_upstream_auth_headers.py

@@ -1,4 +1,6 @@
-from app.services.upstream_client import UpstreamClient
+import pytest
+
+from app.services.upstream_client import UpstreamClient, UpstreamError
 
 
 def test_new_api_token_headers_include_authorization_and_new_api_user():
@@ -16,6 +18,18 @@ def test_new_api_token_headers_include_authorization_and_new_api_user():
     assert "Nox-Api-User" not in headers
 
 
+def test_new_api_token_rejects_dashboard_jwt():
+    client = UpstreamClient(
+        base_url="http://newapi.local",
+        api_prefix="",
+        auth_type="new_api_token",
+        auth_config={"token": "a" * 1200 + ".payload.signature", "user_id": "7"},
+    )
+
+    with pytest.raises(UpstreamError, match="面板登录 JWT"):
+        client._headers()
+
+
 def test_nox_token_headers_include_authorization_and_nox_api_user():
     client = UpstreamClient(
         base_url="http://nox.local",