Describe the Bug:

The "Apply Skills" preprocessing feature has multiple communication issues:

1. getBackgroundTask command not handled - The switch statement in backgroundTask.js is missing the case for "getBackgroundTask", so the current preprocessing state is never returned to clients on page load.
2. No state persistence on refresh - Pressing F5 during preprocessing shows "Apply Skills" button instead of "View Processing" because the state fetch fails.
3. Error messages not displayed - NLP errors are stored server-side but never sent to the frontend for display.
4. No completion summary - Modal closes immediately when preprocessing finishes; users can't see success/failure summary.

Reproducibility:

• Yes
• No
• Sometimes

Steps to Reproduce the Behavior:

1. Navigate to Dashboard → Submissions as admin
2. Click "Apply Skills" and start preprocessing
3. Press F5 to refresh the page while preprocessing is running
4. Observe that the button shows "Apply Skills" instead of "View Processing"
5. Click "Apply Skills" again - able to start another preprocessing (should be blocked)

Expected Behavior:

• On page refresh, button should show "View Processing" if preprocessing is active
• Clicking button should open progress modal showing current preprocessing status
• Error messages should be displayed in the UI
• Completion summary should be shown before modal closes

Actual Behavior:

• Button shows "Apply Skills" after refresh even when preprocessing is running in background
• Users can potentially start duplicate preprocessing tasks
• Errors are logged server-side only, not visible to users
• Modal disappears immediately on completion with no summary

System Information:

• Device (OS/Type): Windows 11
• Browser (+ Version): Chrome Version 143.0.7499.170
• CARE Software (Version/Branch): Project-31-eiwa

Additional Information:

Root cause in backend/webserver/services/backgroundTask.js:
https://github.com/UKPLab/CARE/blob/main/backend/webserver/services/backgroundTask.js#L41