Fixes #680

When location services are disabled and bookmarks are sorted by distance:

• Previously: No bookmarks were shown with a "Location Unavailable" message (see screenshot below)
• Now: Falls back to showing bookmarks sorted by group.

Changes made :

1. Changed listItemsSortedByDistance() to fall back to group sorting when no location
2. Modified items(for:) to automatically fall back to group sorting when location is unavailable
3. Updated emptyData(for:) to only show empty state for actual empty bookmarks

Before (Location Unavailable):