feat: normalize internal system user ID in notification dispatch

- Add SYSTEM_INTERNAL_USER_ID constant and helpers to app.utils.identity
- Ensure internal user ID is normalized to None before dispatching notifications, preventing misrouting to external channels
- Refactor MessageChain to use normalization for all message dispatch methods
- Add tests for internal user ID normalization and notification dispatch behavior

tests/test_system_notification_dispatch.py

@@ -0,0 +1,70 @@
+import sys
+import unittest
+from types import ModuleType
+from unittest.mock import patch
+
+sys.modules.setdefault("qbittorrentapi", ModuleType("qbittorrentapi"))
+setattr(sys.modules["qbittorrentapi"], "TorrentFilesList", list)
+sys.modules.setdefault("transmission_rpc", ModuleType("transmission_rpc"))
+setattr(sys.modules["transmission_rpc"], "File", object)
+sys.modules.setdefault("psutil", ModuleType("psutil"))
+
+from app.chain.message import MessageChain
+from app.schemas import Notification
+from app.utils.identity import (
+    SYSTEM_INTERNAL_USER_ID,
+    is_internal_user_id,
+    normalize_internal_user_id,
+)
+
+
+class TestSystemNotificationDispatch(unittest.TestCase):
+    def test_internal_userid_identity_helpers(self):
+        self.assertTrue(is_internal_user_id(SYSTEM_INTERNAL_USER_ID))
+        self.assertTrue(is_internal_user_id(" System "))
+        self.assertIsNone(normalize_internal_user_id(SYSTEM_INTERNAL_USER_ID))
+        self.assertEqual(normalize_internal_user_id("10001"), "10001")
+
+    def test_post_message_normalizes_internal_userid_before_queueing(self):
+        chain = MessageChain()
+        message = Notification(
+            userid=SYSTEM_INTERNAL_USER_ID,
+            username="admin",
+            title="后台报告",
+            text="任务完成",
+        )
+
+        with patch("app.chain.MessageTemplateHelper.render", return_value=message), patch.object(
+            chain.messagehelper, "put"
+        ), patch.object(chain.messageoper, "add"), patch.object(
+            chain.eventmanager, "send_event"
+        ) as send_event, patch.object(
+            chain.messagequeue, "send_message"
+        ) as send_message:
+            chain.post_message(message)
+
+        event_payload = send_event.call_args.kwargs["data"]
+        queued_message = send_message.call_args.kwargs["message"]
+
+        self.assertIsNone(event_payload["userid"])
+        self.assertIsNone(queued_message.userid)
+        self.assertFalse(send_message.call_args.kwargs["immediately"])
+
+    def test_send_direct_message_normalizes_internal_userid(self):
+        chain = MessageChain()
+        message = Notification(
+            userid=SYSTEM_INTERNAL_USER_ID,
+            username="admin",
+            title="后台报告",
+            text="任务完成",
+        )
+
+        with patch.object(chain, "run_module") as run_module:
+            chain.send_direct_message(message)
+
+        sent_message = run_module.call_args.kwargs["message"]
+        self.assertIsNone(sent_message.userid)
+
+
+if __name__ == "__main__":
+    unittest.main()