feat: add swipe-to-delete individual apps/websites with confirmation

[renjfk]

Add swipe-to-delete functionality for individual apps and websites in usage lists, allowing users to permanently remove all tracking records for specific items.

Details

• Implement swipe-to-delete gesture on UsageListView rows for both apps and websites
• Show destructive confirmation dialog before deletion with clear warning about permanent data loss
• Delete all UsageSession records matching the selected item's identifier across all time periods
• Update UI immediately after confirmation to reflect removal from current and future views
• Invalidate cached data and refresh statistics to show updated totals and charts
• Handle deletion consistently across both daily and weekly view modes
• Use proper SwiftData transaction handling for data integrity
• Provide visual feedback during deletion process (loading state, completion message)