Add min and max volume functionality per player

[OzGav]

FRONTEND CHANGES: music-assistant/frontend#1569
Satisifies: https://github.com/orgs/music-assistant/discussions/3288

Add configurable min/max volume limits per player

Summary

• Adds per-player minimum and maximum volume configuration options (advanced settings under player controls)
• Volume commands (volume_set, volume_up, volume_down) are scaled from the UI’s 0-100 range to the configured min-max range before being sent to the device
• External volume changes (physical buttons, other apps) are reverse-scaled back to 0-100 for reporting, so the UI always displays a consistent 0-100 range
• Group volume adjustments work correctly since scaling is applied per child player
• Config validation rejects min > max to prevent invalid states
• Works with all API clients (frontend, Home Assistant, third-party) without any client-side changes

Edge cases and functionality covered

cmd_volume_set — The 0-100 input is linearly mapped to [min_volume, max_volume] via min_volume + (volume_level * (max_volume - min_volume)) // 100 before reaching the device. Applies to all programmatic and API invocations.

cmd_volume_up / cmd_volume_down — Step-based changes still operate in the 0-100 UI range (step sizes of 1-3 depending on position). Scaling happens downstream in _handle_cmd_volume_set, so no special casing is needed here.

External volume changes — When a device reports a volume change (e.g. user pressed a physical volume button, or used a manufacturer app), signal_player_state_update reverse-scales the reported value back to the 0-100 range before it reaches the UI. This keeps the slider position consistent with user expectations regardless of how the volume was changed.

Group volume — Each child player is scaled independently using its own min_volume/max_volume, so a group volume of 80 translates correctly for each member (e.g. a soundbar with max=50 receives 40, a regular speaker with max=100 receives 80).

Config validation — on_player_config_change validates that min_volume <= max_volume and raises InvalidDataError if not.

Falsy value handling — Uses explicit is not None checks rather than truthiness when reading config values, so min_volume=0 (a valid and common default) isn’t incorrectly treated as missing.

Advanced settings — Both config entries are marked as advanced so they don’t clutter the basic player settings for users who don’t need them.

Default behavior unchanged — With defaults of min=0 and max=100, the scaling formula is the identity function, so all existing behavior is preserved.

[oleost]

Thanks for trying to fix https://github.com/orgs/music-assistant/discussions/3288

Was wondering, would it be possible to implement also a option to scale the volume ?

Something like this:
https://github.com/oleost/server/tree/dev-max-volum-scale

[oleost]

Readjusted the mentioned pull request above to only scale volume.

[marcelveldt]

1. Agreed on scaling the volume - that is imo the only way to implement this properly.
2. Do we really need min volume ? Isn't this always about max volume ?

[oleost]

1. Agreed on scaling the volume - that is imo the only way to implement this properly.

   2. Do we really need min volume ? Isn't this always about max volume ?

For me personally I don't need min volume, however was someone that requested it, and cant see what it hurts implementing it at the same time. Mute still works.