MetroList: Handle Back Gesture in Expanded Player

Problem

Back gesture wasn't handled correctly when the player was in expanded view. Users couldn't dismiss the expanded player using system back gesture, requiring them to tap the collapse button instead.

Solution

Implemented back gesture handling in the expanded player state, properly routing the back event to collapse the player before handling navigation.

Result

Back gesture works correctly in expanded player, providing consistent navigation behavior across all player states.

Commit: MetrolistGroup/Metrolist@1d1a105
PR: #3433