Features:
- Asset preview thumbnails in results grid: inline 40×40 thumb for images,
  kind badge (PDF, VIDEO, etc.) for other file types
- Hover tooltip on image rows shows a larger preview (up to 220×150)
- Prominent scan timestamp in the results header
- Amber stale badge when scan results are older than 24 hours
- Recommendation banner above bulk actions advising to ZIP backup or use
  Trash before permanently deleting assets

Fixes:
- Fix CSV export timeout on large datasets (issue #3): export now reads from
  cached queue results instead of re-running a full synchronous scan
- Fix broken translations: all UI strings in the utility page now go through
  Craft's translation system — nothing was reaching the translation files before
- CSV filename now uses the actual scan datetime, not the download datetime
- CLI export (php craft asset-cleaner/scan/export) now matches web CSV exactly:
  same columns (ID, Title, Filename, Volume, Size, Path, URL), same filename
  pattern, and fixed a silent bug where Date Created column always produced
  empty values (field does not exist in asset data)
- Fix fatal crash in CLI export when using --volumes flag (sanitizeFilename
  method was missing from ScanController)