Nav2导航 + 初始化位置功能

- nav2_navigator.py: 通过 ros2 action 与 Nav2 通信，修复 YAML 格式（pose 嵌套）
- mission_executor.py: 改用 Nav2 navigate_to_pose action 导航
- app.py: navigate/to 等 API 改用 Nav2Navigator；新增 /api/mission/init_pose
  API，通过子进程调用 rclpy 发布 /initialpose 到 (0,0,0)
- setting.html/js: 任务配置Tab加「初始化位置」按钮

注意：ROS2 daemon (domain=1) 与 Flask 在不同 domain，
Flask 进程内调用 rclpy 会破坏 daemon 状态，需通过子进程调用

agv_app/utils/mission_executor.py

@@ -250,15 +250,16 @@ class MissionExecutor:
             f"      sec: 0\n"
             f"      nanosec: 0\n"
             f"    frame_id: 'map'\n"
-            f"  position:\n"
-            f"    x: {x}\n"
-            f"    y: {y}\n"
-            f"    z: 0.0\n"
-            f"  orientation:\n"
-            f"    x: 0.0\n"
-            f"    y: 0.0\n"
-            f"    z: {qz}\n"
-            f"    w: {qw}"
+            f"  pose:\n"
+            f"    position:\n"
+            f"      x: {x}\n"
+            f"      y: {y}\n"
+            f"      z: 0.0\n"
+            f"    orientation:\n"
+            f"      x: 0.0\n"
+            f"      y: 0.0\n"
+            f"      z: {qz}\n"
+            f"      w: {qw}"
         )
 
         logger.info(f"Nav2 发送导航目标: ({x:.3f}, {y:.3f}), yaw={math.degrees(yaw):.1f}°")
@@ -266,7 +267,7 @@ class MissionExecutor:
         # 发送 goal 并监听反馈和结果
         cmd = (
             f"ros2 action send_goal /navigate_to_pose "
-            f"navigation_action_msgs/NavigateToPose "
+            f"nav2_msgs/action/NavigateToPose "
             f"'{pose_yaml}' "
             f"--feedback"
         )