feat: 管理后台UI全面优化 + TCP指令发送修复

- 指令页面：三个设备选择器合并为顶部统一选择器，在线/离线分组显示
- 仪表盘：8卡片压缩为6紧凑卡片，新增刷新按钮和更新时间戳
- 仪表盘：最近告警添加"查看全部"跳转链接
- 考勤页面：定位方式显示GPS/WiFi/LBS文字标签替代纯图标
- 告警页面：alarm_source中文化(单围栏/多围栏/基站/WiFi)
- 告警页面：确认操作改为DOM单行更新，无需刷新整个表格
- 数据日志：默认选中"位置"类型
- 全部表格：全选复选框tooltip改为"全选当前页"
- TCP修复：移除发送前硬性在线检查，改为尝试发送+失败提示
- TCP修复：检测僵死连接(writer.is_closing)并自动清理

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

app/tcp_server.py

@@ -2445,6 +2445,13 @@ class TCPManager:
             return False
 
         _reader, writer, conn_info = conn
+
+        # Check if the writer is still alive
+        if writer.is_closing():
+            logger.warning("IMEI=%s writer is closing, removing stale connection", imei)
+            del self.connections[imei]
+            return False
+
         serial = conn_info.next_serial()
 
         # Build 0x80 online-command packet
@@ -2469,7 +2476,8 @@ class TCPManager:
                 command_content,
             )
         except Exception:
-            logger.exception("Failed to send command to IMEI=%s", imei)
+            logger.exception("Failed to send command to IMEI=%s, removing stale connection", imei)
+            self.connections.pop(imei, None)
             return False
 
         return True
@@ -2495,6 +2503,12 @@ class TCPManager:
             return False
 
         _reader, writer, conn_info = conn
+
+        if writer.is_closing():
+            logger.warning("IMEI=%s writer is closing, removing stale connection", imei)
+            del self.connections[imei]
+            return False
+
         serial = conn_info.next_serial()
 
         msg_bytes = message.encode("utf-16-be")
@@ -2517,7 +2531,8 @@ class TCPManager:
             logger.info("Message sent to IMEI=%s (%d bytes)", imei, len(msg_bytes))
             return True
         except Exception:
-            logger.exception("Failed to send message to IMEI=%s", imei)
+            logger.exception("Failed to send message to IMEI=%s, removing stale connection", imei)
+            self.connections.pop(imei, None)
             return False
 
     # ------------------------------------------------------------------