Add configurable auto-sleep timeout in Settings with options: - 1 minute - 5 minutes - 10 minutes (default) - 15 minutes - 30 minutes Changes: - Add SLEEP_TIMEOUT enum and sleepTimeout field to CrossPointSettings - Add getSleepTimeoutMs() helper method - Add sleepTimeout to settings serialization - Add 'Time to Sleep' option in SettingsActivity - Replace hardcoded AUTO_SLEEP_TIMEOUT_MS with SETTINGS.getSleepTimeoutMs()