fix(import): fail auto import on drive auth failure

tests/test_auto_import_failure_boundaries.py

@@ -143,3 +143,50 @@ def test_auto_import_does_not_move_drive_file_when_import_fails(monkeypatch, tmp
     assert result["success"] is False
     assert result["failed_count"] == 1
     assert fake_drive.moved_files == []
+
+
+def test_auto_import_fails_closed_when_drive_auth_fails(monkeypatch, tmp_path):
+    import_service = _load_import_service(monkeypatch, f"sqlite:///{tmp_path / 'momo.db'}")
+    import_service.Base.metadata.create_all(import_service.engine)
+
+    class FakeDriveService:
+        last_error_kind = "authentication_failed"
+        last_error = "could not locate runnable browser"
+
+        def list_files_in_folder(self, folder_path, file_pattern):
+            return []
+
+    monkeypatch.setattr(import_service, "drive_service", FakeDriveService())
+
+    service = import_service.ImportService()
+    result = service.auto_import_from_drive()
+
+    assert result["success"] is False
+    assert result["file_count"] == 0
+    assert result["imported_count"] == 0
+    assert result["failed_count"] == 1
+    assert result["connection_error"] is True
+    assert result["error_kind"] == "authentication_failed"
+    assert "Google Drive" in result["message"]
+    assert "could not locate runnable browser" in result["message"]
+
+
+def test_auto_import_empty_drive_folder_remains_success(monkeypatch, tmp_path):
+    import_service = _load_import_service(monkeypatch, f"sqlite:///{tmp_path / 'momo.db'}")
+    import_service.Base.metadata.create_all(import_service.engine)
+
+    class FakeDriveService:
+        last_error_kind = None
+        last_error = None
+
+        def list_files_in_folder(self, folder_path, file_pattern):
+            return []
+
+    monkeypatch.setattr(import_service, "drive_service", FakeDriveService())
+
+    service = import_service.ImportService()
+    result = service.auto_import_from_drive()
+
+    assert result["success"] is True
+    assert result["file_count"] == 0
+    assert result["message"] == "沒有找到待匯入的檔案"