[beta] MacOS volume control for WiiM

[v-kooistra]

Works fine but would be nice if I change volume on the master of a group it changes the group volume.

​

I've not implemented group control yet. how would we like to do it? :

1. Absolute Volume :

• Master volume = 50 → All slaves = 50
• Simple and predictable
• All speakers play at exact same level

2. Relative Volume (What native app might does?):

• If master goes up by +10, all slaves go up by +10
• Preserves individual volume differences
• Example: Master at 50, Slave at 30. Increase master by 10 → Master becomes 60, Slave becomes 40
  

let me know what I should buiid.