feat: 高德IoT v5 API升级、电子围栏管理、设备绑定自动考勤

- 前向地理编码升级为高德IoT v5 API (POST restapi.amap.com/v5/position/IoT)
- 修复LBS定位偏差: 添加network=LTE参数区分4G/2G, bts格式补充cage字段
- 新增电子围栏管理模块 (circle/polygon/rectangle), 支持地图绘制和POI搜索
- 新增设备-围栏多对多绑定 (DeviceFenceBinding/DeviceFenceState)
- 围栏自动考勤引擎 (fence_checker.py): haversine距离、ray-casting多边形判定、容差机制、防抖
- TCP位置上报自动检测围栏进出, 生成考勤记录并WebSocket广播
- 前端围栏页面: 绑定设备弹窗、POI搜索定位、左侧围栏面板
- 新增fence_attendance WebSocket topic

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

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

app/websocket_manager.py

@@ -6,7 +6,7 @@ Manages client connections, topic subscriptions, and broadcasting.
 import asyncio
 import json
 import logging
-from datetime import datetime, timezone
+from app.config import now_cst
 
 from fastapi import WebSocket
 
@@ -16,7 +16,7 @@ logger = logging.getLogger(__name__)
 MAX_CONNECTIONS = 100
 
 # Valid topics
-VALID_TOPICS = {"location", "alarm", "device_status", "attendance", "bluetooth"}
+VALID_TOPICS = {"location", "alarm", "device_status", "attendance", "bluetooth", "fence_attendance"}
 
 
 class WebSocketManager:
@@ -57,7 +57,7 @@ class WebSocketManager:
             return
 
         message = json.dumps(
-            {"topic": topic, "data": data, "timestamp": datetime.now(timezone.utc).isoformat()},
+            {"topic": topic, "data": data, "timestamp": now_cst().isoformat()},
             default=str,
             ensure_ascii=False,
         )