- Add SettingsCache with TTL-based invalidation (30 seconds)
- Cache scan_poll_interval_seconds and auto_scan_enabled settings
- Reduce database queries from every poll/check to once per TTL period
- Improve error handling with proper fallback values
- Simplify boolean parsing with strings.ToLower for consistency
This optimization reduces database load when checking scan settings,
which occurs frequently during media scanning operations.
