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/order_tools.py

@@ -0,0 +1,149 @@
+"""
+工单工具：查询我的工单、提交处理结果
+"""
+
+import json
+from typing import List, Optional
+from langchain_core.tools import tool
+from langchain_core.runnables import RunnableConfig
+
+from app.utils.logger import logger
+from .alarm_query import ALARM_TYPE_NAMES, _get_camera_display_name
+from .alarm_action import _get_order_id_for_alarm
+
+
+@tool
+def list_my_orders(config: RunnableConfig, status: str = "HANDLING") -> str:
+    """查询我的待处理工单列表
+
+    Args:
+        status: 工单状态筛选 HANDLING=处理中 ALL=全部
+    """
+    from app.services.alarm_event_service import get_alarm_event_service
+    svc = get_alarm_event_service()
+
+    user_id = config.get("configurable", {}).get("user_id", "")
+
+    alarms, total = svc.get_alarms(
+        alarm_status="CONFIRMED",
+        page=1,
+        page_size=20,
+    )
+
+    my_alarms = [a for a in alarms if a.handler == user_id]
+
+    if not my_alarms:
+        return json.dumps({"total": 0, "items": [], "message": "当前没有待处理的工单"}, ensure_ascii=False)
+
+    items = []
+    for a in my_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,
+            "time": event_time,
+        })
+
+    return json.dumps({"total": len(my_alarms), "items": items}, ensure_ascii=False)
+
+
+@tool
+async def submit_order_result(
+    alarm_id: str,
+    result_text: str,
+    config: RunnableConfig,
+    image_urls: Optional[List[str]] = None,
+) -> str:
+    """提交工单处理结果（文字描述+处理后照片URL）
+
+    Args:
+        alarm_id: 关联的告警ID
+        result_text: 处理结果描述
+        image_urls: 处理后照片URL列表（COS永久URL）
+    """
+    from app.services.alarm_event_service import get_alarm_event_service
+    from app.services.wechat_service import get_wechat_service
+
+    user_id = config.get("configurable", {}).get("user_id", "")
+    svc = get_alarm_event_service()
+    wechat = get_wechat_service()
+
+    if image_urls is None:
+        image_urls = []
+
+    # 检查告警是否存在
+    detail = svc.get_alarm(alarm_id)
+    if not detail:
+        return json.dumps({"error": f"未找到告警: {alarm_id}"}, ensure_ascii=False)
+
+    # 合并 session 中暂存的图片
+    from app.services.session_manager import get_session_manager
+    session = get_session_manager().get(user_id)
+    if session.pending_images:
+        image_urls = session.pending_images + image_urls
+        session.pending_images = []
+
+    # 获取关联工单ID
+    order_id = _get_order_id_for_alarm(alarm_id)
+
+    from app.services.work_order_client import get_work_order_client
+    wo_client = get_work_order_client()
+
+    remark = f"企微Agent结单: {result_text}"
+    if image_urls:
+        remark += f" (附{len(image_urls)}张图片)"
+
+    if order_id and wo_client.enabled:
+        if not await wo_client.submit_order(
+            order_id,
+            result=f"{result_text} by {user_id}",
+            result_img_urls=image_urls or None,
+        ):
+            remark += "(IoT降级)"
+
+    svc.handle_alarm(alarm_id=alarm_id, alarm_status="CLOSED",
+                     handle_status="DONE", handler=user_id, remark=remark)
+
+    # 持久化处理结果图片到 alarm_event_ext
+    if image_urls:
+        try:
+            from app.models import get_session as get_db_session, AlarmEventExt
+            db = get_db_session()
+            try:
+                ext = AlarmEventExt(
+                    alarm_id=alarm_id,
+                    ext_type="HANDLER_RESULT",
+                    ext_data={"result_text": result_text, "image_urls": image_urls, "handler": user_id},
+                )
+                db.add(ext)
+                db.commit()
+            except Exception as e:
+                db.rollback()
+                logger.error(f"持久化处理结果图片失败: {e}")
+            finally:
+                db.close()
+        except Exception as e:
+            logger.error(f"保存处理结果失败: {e}")
+
+    # 更新卡片到终态
+    response_code = wechat.get_response_code(alarm_id)
+    if response_code:
+        await wechat.update_alarm_card_terminal(
+            response_code=response_code, user_ids=[user_id],
+            alarm_id=alarm_id, action="complete", operator_name=user_id,
+        )
+
+    result = {
+        "success": True,
+        "message": f"工单已提交: {alarm_id}",
+        "result": result_text,
+        "images_count": len(image_urls),
+    }
+    return json.dumps(result, ensure_ascii=False)