重构 Agent：引入 LangGraph StateGraph 替代手写 FC 循环

架构变更：
- 新增 app/services/agent/ 模块（state/prompts/graph/tools）
- 7 个工具从 _tool_xxx 方法提取为 @tool 装饰器函数
- 构建 assistant + ToolNode 的 ReAct 图
- agent_dispatcher.py 改为薄壳入口，支持 USE_LANGGRAPH 开关
- MemorySaver checkpoint 持久化对话（thread_id=wechat-{user_id}）
- 新增依赖：langchain-core, langchain-openai, langgraph

向后兼容：
- USE_LANGGRAPH=false 可切回旧版 FC 循环
- LangGraph 初始化失败自动降级到 Legacy 模式
- 企微图片处理/VLM分析逻辑不变

app/services/agent/tools/alarm_query.py

@@ -0,0 +1,196 @@
+"""
+告警查询工具：统计、列表、详情
+"""
+
+import json
+from datetime import timedelta
+from typing import Optional
+from langchain_core.tools import tool
+from langchain_core.runnables import RunnableConfig
+
+from app.utils.logger import logger
+from app.utils.timezone import beijing_now
+
+
+# 告警类型/级别/状态 中文映射
+ALARM_TYPE_NAMES = {
+    "leave_post": "人员离岗", "intrusion": "周界入侵",
+    "illegal_parking": "车辆违停", "vehicle_congestion": "车辆拥堵",
+}
+ALARM_LEVEL_NAMES = {0: "紧急", 1: "重要", 2: "普通", 3: "轻微"}
+ALARM_STATUS_NAMES = {
+    "NEW": "待处理", "CONFIRMED": "处理中",
+    "FALSE": "误报", "CLOSED": "已关闭",
+}
+
+
+def _parse_time_range(time_range: str):
+    """解析时间范围，返回 (start_time, label)"""
+    now = beijing_now()
+    if time_range == "week":
+        start = now - timedelta(days=now.weekday())
+        start = start.replace(hour=0, minute=0, second=0, microsecond=0)
+        return start, "本周"
+    elif time_range == "month":
+        start = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
+        return start, "本月"
+    else:
+        start = now.replace(hour=0, minute=0, second=0, microsecond=0)
+        return start, "今日"
+
+
+def _get_camera_display_name(device_id: str) -> str:
+    """同步获取摄像头显示名称"""
+    try:
+        import asyncio
+        from app.services.camera_name_service import get_camera_name_service
+        camera_service = get_camera_name_service()
+        loop = asyncio.get_event_loop()
+        if loop.is_running():
+            import concurrent.futures
+            with concurrent.futures.ThreadPoolExecutor() as pool:
+                cam_info = pool.submit(
+                    asyncio.run, camera_service.get_camera_info(device_id)
+                ).result(timeout=5)
+        else:
+            cam_info = asyncio.run(camera_service.get_camera_info(device_id))
+        return camera_service.format_display_name(device_id, cam_info)
+    except Exception:
+        return device_id
+
+
+@tool
+def query_alarm_stats(time_range: str = "today", alarm_type: str = "all") -> str:
+    """查询告警统计数据（总数、按类型分布、按状态分布）
+
+    Args:
+        time_range: 时间范围 today=今日 week=本周 month=本月
+        alarm_type: 告警类型筛选 leave_post/intrusion/illegal_parking/vehicle_congestion/all
+    """
+    from app.services.alarm_event_service import get_alarm_event_service
+    svc = get_alarm_event_service()
+
+    start, range_label = _parse_time_range(time_range)
+    now = beijing_now()
+
+    alarm_type_filter = None if alarm_type == "all" else alarm_type
+
+    alarms, total = svc.get_alarms(
+        alarm_type=alarm_type_filter,
+        start_time=start,
+        end_time=now,
+        page=1,
+        page_size=10000,
+    )
+
+    type_count = {}
+    status_count = {"NEW": 0, "CONFIRMED": 0, "FALSE": 0, "CLOSED": 0}
+    for a in alarms:
+        type_count[a.alarm_type] = type_count.get(a.alarm_type, 0) + 1
+        if a.alarm_status in status_count:
+            status_count[a.alarm_status] += 1
+
+    result = {
+        "range": range_label,
+        "total": total,
+        "by_type": {ALARM_TYPE_NAMES.get(t, t): c for t, c in type_count.items()},
+        "by_status": {ALARM_STATUS_NAMES.get(s, s): c for s, c in status_count.items()},
+    }
+    return json.dumps(result, ensure_ascii=False)
+
+
+@tool
+def list_alarms(
+    time_range: str = "today",
+    alarm_type: str = "all",
+    alarm_status: str = "",
+    limit: int = 10,
+) -> str:
+    """查询告警列表，返回最近的告警记录（含ID、类型、摄像头、状态、时间）
+
+    Args:
+        time_range: 时间范围 today/week/month
+        alarm_type: 告警类型筛选 leave_post/intrusion/illegal_parking/vehicle_congestion/all
+        alarm_status: 告警状态筛选 NEW=待处理 CONFIRMED=处理中 FALSE=误报 CLOSED=已关闭
+        limit: 返回条数，默认10，最多20
+    """
+    from app.services.alarm_event_service import get_alarm_event_service
+    svc = get_alarm_event_service()
+
+    start, range_label = _parse_time_range(time_range)
+    now = beijing_now()
+
+    alarm_type_filter = None if alarm_type == "all" else alarm_type
+    status_filter = alarm_status if alarm_status else None
+    limit = min(limit, 20)
+
+    alarms, total = svc.get_alarms(
+        alarm_type=alarm_type_filter,
+        alarm_status=status_filter,
+        start_time=start,
+        end_time=now,
+        page=1,
+        page_size=limit,
+    )
+
+    items = []
+    for a in alarms:
+        cam_name = _get_camera_display_name(a.device_id)
+        event_time = ""
+        if a.event_time:
+            try:
+                event_time = a.event_time.strftime("%m-%d %H:%M")
+            except Exception:
+                event_time = str(a.event_time)[:16]
+        items.append({
+            "alarm_id": a.alarm_id,
+            "type": ALARM_TYPE_NAMES.get(a.alarm_type, a.alarm_type),
+            "camera": cam_name,
+            "status": ALARM_STATUS_NAMES.get(a.alarm_status, a.alarm_status),
+            "level": ALARM_LEVEL_NAMES.get(a.alarm_level, "普通"),
+            "time": event_time,
+        })
+
+    result = {"range": range_label, "total": total, "items": items}
+    return json.dumps(result, ensure_ascii=False)
+
+
+@tool
+def get_alarm_detail(alarm_id: str, config: RunnableConfig) -> str:
+    """查询单条告警的详细信息（含扩展信息和AI分析结果）
+
+    Args:
+        alarm_id: 告警ID（如 edge_xxx 或 ALM_xxx）
+    """
+    from app.services.alarm_event_service import get_alarm_event_service
+    svc = get_alarm_event_service()
+
+    detail = svc.get_alarm(alarm_id)
+    if not detail:
+        return json.dumps({"error": f"未找到告警: {alarm_id}"}, ensure_ascii=False)
+
+    snapshot_url = detail.get("snapshot_url", "")
+
+    result = {
+        "alarm_id": detail.get("alarm_id"),
+        "alarm_type": ALARM_TYPE_NAMES.get(detail.get("alarm_type", ""), detail.get("alarm_type", "")),
+        "device_id": detail.get("device_id"),
+        "alarm_status": ALARM_STATUS_NAMES.get(detail.get("alarm_status", ""), detail.get("alarm_status", "")),
+        "alarm_level": ALARM_LEVEL_NAMES.get(detail.get("alarm_level"), "普通"),
+        "event_time": str(detail.get("event_time", ""))[:19],
+        "handle_status": detail.get("handle_status"),
+        "handler": detail.get("handler"),
+        "has_snapshot": bool(snapshot_url),
+        "snapshot_url": snapshot_url,
+    }
+
+    # 摄像头名称
+    result["camera_name"] = _get_camera_display_name(detail.get("device_id", ""))
+
+    # LLM 分析
+    analyses = detail.get("llm_analyses", [])
+    if analyses:
+        latest = analyses[-1]
+        result["ai_analysis"] = latest.get("summary", "")
+
+    return json.dumps(result, ensure_ascii=False)