Nav2 导航集成：新增 nav2_navigator.py，mission_executor 改用 Nav2 action 导航

- 新增 agv_app/utils/nav2_navigator.py：Nav2Navigator 类，通过 ros2 action
  /navigate_to_pose 和 /navigate_through_poses 与 Nav2 通信，支持路径点导航
- app.py：navigate/to, navigate/path, navigate/status 三个 API 改用 Nav2Navigator
- mission_executor.py：_execute_point 中调用 _nav2_go_to_point() 替代原来的
  time.sleep 模拟移动，Nav2 负责从当前点到目标点的自主导航
- 原有的 map_navigator.py（A* + Pure Pursuit 自实现）保留不动，供无 Nav2 时降级用

agv_app/data/models_config.json

@@ -0,0 +1,71 @@
+[
+  {
+    "id": "m_1778767289",
+    "name": "机型1",
+    "serial_prefix": "",
+    "poses": [
+      {
+        "id": "pose_1778767302",
+        "name": "front_1",
+        "photo_type": "front",
+        "arm_angles": [
+          0,
+          0,
+          0,
+          0,
+          0,
+          0
+        ],
+        "speed": 500,
+        "description": ""
+      },
+      {
+        "id": "pose_1778767312",
+        "name": "front_2",
+        "photo_type": "front",
+        "arm_angles": [
+          0,
+          0,
+          0,
+          0,
+          0,
+          0
+        ],
+        "speed": 500,
+        "description": ""
+      },
+      {
+        "id": "pose_1778767323",
+        "name": "back_1",
+        "photo_type": "back",
+        "arm_angles": [
+          0,
+          0,
+          0,
+          0,
+          0,
+          0
+        ],
+        "speed": 500,
+        "description": ""
+      },
+      {
+        "id": "pose_1778767325",
+        "name": "back_2",
+        "photo_type": "back",
+        "arm_angles": [
+          0,
+          0,
+          0,
+          0,
+          0,
+          0
+        ],
+        "speed": 500,
+        "description": ""
+      }
+    ],
+    "description": "",
+    "notes": ""
+  }
+]