Display the task's current position in the queue

[julien-nc]

• Requires [taskprocessing] Add an endpoint to get the position of a scheduled task in the queue server#62414

Poll the selected task's position every 5 seconds. Display it in the "loading" empty content.

• In the loading empty content

• In the chat UI

Todo

• Adjust the message
• Improve design

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI