Add required restart trigger node and wire /phenaix/controller restart button with confirmation

[Copilot]

This change adds a controller-side Restart action that cleanly terminates the ROS 2 launch context. It does so by introducing a dedicated trigger-service node and marking it as required in launch so its exit shuts down the full system.

• Launch lifecycle integration

  • Added a new restart_service_node process to viewer.launch.py.
  • Configured it with on_exit=Shutdown(...) so exiting this node stops the entire launch tree.

• New restart trigger service node

  • Added ros2_web_viewer/restart_service_node.py.
  • Exposes std_srvs/Trigger service at /restart_system.
  • On successful request, it returns a trigger response and then shuts down its rclpy context to exit the process.

• Packaging / executable wiring

  • Registered new console entry point in setup.py:
    • restart_service_node = ros2_web_viewer.restart_service_node:main

• Controller UI update

  • Added a Restart button to web/phenaix/controller.html.
  • Wired via existing trigger bridge attributes:
    • data-trigger-service="/restart_system"
  • Added confirmation gating for restart:
    • data-trigger-confirm="Restart the system now?"
    • Clicking Restart opens a confirmation popup.
    • Confirm proceeds with the trigger call.
    • Cancel/close dismisses the popup without calling restart.

• Frontend trigger handling update

  • Updated web/app.js so buttons with data-trigger-confirm require explicit user confirmation before calling /api/trigger.

• Docs update

  • Updated README trigger-button section to note the default /restart_system behavior and required-node shutdown semantics.

<button
  class="ctrl-btn ctrl-btn-restart"
  data-trigger-service="/restart_system"
  data-trigger-confirm="Restart the system now?"
  data-trigger-timeout="2"
  data-trigger-cooldown="3">
  Restart
</button>

https://github.com/user-attachments/assets/a1abe134-c8d6-4f8f-889c-b507f39fd58b

[marc-hanheide]

change the logic for the restart button so that the actual restart needs confirmation by the user. Clicking the main restart button should open a pop up with a question if a restart should really be carried out, and on the button confirming the restart should actually trigger the restart while closing the popup or declining the restart should just close the popup.

[Copilot]

Implemented in commit 3fdc33e. Restart now requires user confirmation: the Restart button opens a confirmation popup (Restart the system now?), and only confirming proceeds with the trigger call; cancel/close dismisses without calling restart. Screenshot: https://github.com/user-attachments/assets/a1abe134-c8d6-4f8f-889c-b507f39fd58b