fix: 系统监控改用 asyncio task 驱动，抗 Android 后台挂起

- SystemMonitor/PluginStatusPanel: 移除 set_interval, 改用外部 refresh()
- TuiService._refresh_monitors(): asyncio.sleep(2) 循环刷新
- asyncio.sleep 在 Android 恢复前台后能正常续跑
- shutdown 时 cancel refresh task

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

services/tui_service.py

@@ -425,10 +425,9 @@ class SystemMonitor(Static):
     def set_collector(self, c):
         self._collector = c
 
-    def on_mount(self):
-        self._timer = self.set_interval(2, self._refresh_stats)
-
-    def _refresh_stats(self):
+    def refresh(self):
+        """由外部 asyncio task 驱动刷新（比 set_interval 更抗 Android 挂起）"""
+        self._refresh_stats()
         try:
             if not self._collector:
                 self.update("📊 系统监控: 数据源未连接")
@@ -477,12 +476,13 @@ class PluginStatusPanel(Static):
         self._plugin_service = plugin_service
         self._timer = None
 
-    def on_mount(self):
-        self._timer = self.set_interval(3, self._refresh)
-
     def set_plugin_service(self, svc):
         self._plugin_service = svc
 
+    def refresh(self):
+        """由外部 asyncio task 驱动刷新"""
+        self._refresh()
+
     def _refresh(self):
         try:
             if not self._plugin_service:
@@ -784,7 +784,10 @@ class TuiService:
 
             # 启动消息处理任务
             self._message_processor_task = asyncio.create_task(self._process_message_queue())
-                        
+
+            # 启动后台刷新任务 (asyncio.sleep 比 set_interval 更抗 Android 挂起)
+            self._refresh_task = asyncio.create_task(self._refresh_monitors())
+
             # 在后台运行TUI
             asyncio.create_task(self._run_tui())
             
@@ -850,6 +853,17 @@ class TuiService:
         except Exception as e:
             logger.error(f"消息处理任务出错: {str(e)}")
 
+    async def _refresh_monitors(self):
+        """后台刷新系统监控 + 插件面板 (asyncio.sleep, Android 挂起后可恢复)"""
+        try:
+            while True:
+                if self.tui_app:
+                    self.tui_app.system_monitor.refresh()
+                    self.tui_app.plugin_panel.refresh()
+                await asyncio.sleep(2)
+        except asyncio.CancelledError:
+            logger.debug("监控刷新任务被取消")
+
     def _setup_title(self):
         """设置TUI标题"""
         try:
@@ -886,6 +900,8 @@ class TuiService:
     def shutdown(self):
         """关闭TUI服务"""
         try:
+            if hasattr(self, '_refresh_task') and self._refresh_task:
+                self._refresh_task.cancel()
             if self.tui_app:
                 self.tui_app.shutdown()
             print("TUI服务已关闭")