feat(scan): add bulk delete functionality for saved scans

[DevOlabode]

Implement a new API endpoint DELETE /api/scans to remove all saved scan reports while retaining the account storage. Update the ScanController and storageService to handle the deletion logic, including necessary authentication checks and error handling. Enhance the frontend with a confirmation dialog for users to delete all scans, ensuring a smooth user experience. Update documentation to reflect the new functionality.

closes #110

[ieliofficial]

Backend is right, DELETE /api/scans, the storageService half, the tests. Keep all of it.

The frontend I don't. A Delete all button in Account deletes things you can't see from where you're standing. #119 is the shape: checkboxes on the Dashboard list, select all at the top, same confirm. That also gives partial delete, which people ask for more often.

Move the UI to DashboardView and point this at #119. I'll close #110 as covered.

[DevOlabode]

Just to confirm based on the recent discussion: are we planning to completely remove the "Delete all scans" functionality on the account page and replace it with the checkbox-based bulk deletion from #119?

I want to make sure I understand the intended direction before making any further changes.