MetroList: startForegroundService for Background-safe Service Startup

Problem

Android 15 enforces stricter background service restrictions. MetroList's music service could fail to start when launched from background contexts without proper foreground service preparation.

Solution

Changed service startup to use startForegroundService() with appropriate notification for all background-triggered starts. Ensured service reaches foreground state within the required timeframe.

Result

MetroList works correctly on Android 15 with proper background service handling.

Commit: MetrolistGroup/Metrolist@ac7020a
PR: #3442