Add Automatic Database Backups

[foxintheloop]

Problem

No automatic backups exist. If the database becomes corrupted, all user data is lost.

Solution

Implement daily backup using SQLite's backup API (better-sqlite3 supports db.backup()):

1. On app startup, check if last backup is >24 hours old
2. Use db.backup(backupPath) to create incremental backup
3. Keep last 3-5 backups in the app data directory, rotating old ones
4. Add "Restore from Backup" option in Settings UI
5. Show backup status in settings (last backup time, backup size)

Files

• apps/electron/src/main/database.ts — add backup logic
• apps/electron/src/main/settings.ts — store backup preferences
• apps/electron/src/renderer/components/Settings.tsx — add restore UI