[PR #815] Drive: brand flat folder and file icons

Release Notes

Summary

Drive now uses updated folder and file icons that align with
Stellarbridge branding. The visual refresh applies across Drive folder
and file views, including empty folders.

Changes

• Replaced generic folder and file icons with custom flat-style icons
  in brand green tones.
• Updated file extension badges to use theme-aware accent colors for
  better readability in light and dark modes.
• Icon appearance updates apply to folder listings, file listings, and
  the empty-folder state.

Impact

No customer action required.

Classification

UI