fix:[FL-143][处理消息查看报错]

Co-authored-by: multica-agent <github@multica.ai>

api/tests/test_system_message_schema.py

@@ -0,0 +1,25 @@
+from __future__ import annotations
+
+from datetime import datetime
+from types import SimpleNamespace
+
+from app.schemas.system_message import SystemMessagePublic
+
+
+def test_system_message_public_validates_attribute_object() -> None:
+    message = SimpleNamespace(
+        id="message-1",
+        title="系统通知",
+        content="测试内容",
+        message_type="info",
+        target_user_id=None,
+        is_read=False,
+        created_at=datetime(2026, 1, 1, 12, 0, 0),
+        read_at=None,
+    )
+
+    result = SystemMessagePublic.model_validate(message)
+
+    assert result.id == "message-1"
+    assert result.title == "系统通知"
+    assert result.is_read is False