feat: show progress feedback while repairing root mount #737

Description

When using Repair root mount for a mounted app, there is currently no visible indication that the repair process is actually running.

For example, on the app info page, pressing Repair root mount starts the process, but the UI does not show any progress or status while the repair is being performed. The only feedback appears at the very end, when it either reports that the mount was successfully repaired or that the operation failed.

Proposed improvement

Add a Snackbar or similar temporary progress/status indicator when Repair root mount is started.

For example:

• "Repairing root mount..."
• "Repairing root mount (step 1/...)..." if progress stages are available
• "Root mount repaired successfully"
• "Failed to repair root mount"

The indicator should appear immediately after pressing Repair root mount and remain visible while the operation is in progress. It could then update to the final success or failure state when the operation finishes.

Motivation

At the moment, there is no way to tell whether the repair operation has actually started, is still running, or has become stuck. The user has to wait until the final result appears without any intermediate feedback.

A Snackbar or progress indicator would make the operation's state much clearer and provide immediate confirmation that the repair process is running.