refactor: 移除企微Webhook机器人代码，修复VLM日志

- 删除 wechat_service.send_webhook_alarm 方法
- 删除 config.py 中 webhook_url 配置
- 简化 notify_dispatch 通知逻辑（仅保留应用消息）
- 修复 vlm_service 使用项目统一 logger
- 添加 VLM 调用 URL 调试日志

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/services/wechat_service.py

@@ -176,51 +176,6 @@ class WeChatService:
             logger.error(f"发送文本消息异常: {e}")
             return False
 
-    async def send_webhook_alarm(
-        self,
-        webhook_url: str,
-        alarm_id: str,
-        alarm_type: str,
-        area_name: str,
-        camera_name: str,
-        description: str,
-        event_time: str,
-        alarm_level: int = 2,
-        detail_url: str = "",
-    ) -> bool:
-        """通过群机器人 Webhook 发送告警通知（无需IP白名单）"""
-        type_names = {"leave_post": "人员离岗", "intrusion": "周界入侵"}
-        level_names = {1: "提醒", 2: "一般", 3: "严重", 4: "紧急"}
-
-        type_name = type_names.get(alarm_type, alarm_type)
-        level_name = level_names.get(alarm_level, "一般")
-
-        content = (
-            f"## 【{level_name}】{type_name}告警\n"
-            f"> 区域：<font color=\"warning\">{area_name}</font>\n"
-            f"> 摄像头：{camera_name}\n"
-            f"> 时间：{event_time}\n"
-            f"> AI描述：**{description}**\n"
-        )
-        if detail_url:
-            content += f"> [查看详情]({detail_url})\n"
-
-        msg = {"msgtype": "markdown", "markdown": {"content": content}}
-
-        try:
-            async with httpx.AsyncClient(timeout=10) as client:
-                resp = await client.post(webhook_url, json=msg)
-                data = resp.json()
-            if data.get("errcode") != 0:
-                logger.error(f"Webhook发送失败: {data}")
-                return False
-            logger.info(f"Webhook告警已发送: alarm={alarm_id}")
-            return True
-        except Exception as e:
-            logger.error(f"Webhook发送异常: {e}")
-            return False
-
-
 # 全局单例
 _wechat_service: Optional[WeChatService] = None