chore(deps): migrate kira 0.9 → 0.12

- Import paths simplified: manager/tween modules re-exported from kira root
  (AudioManager, AudioManagerSettings, DefaultBackend, Tween all via kira::*)
- Volume::Amplitude removed; replaced with Value<Decibels> using a new
  amplitude_to_decibels() helper (20*log10 conversion, clamps to SILENCE)
- output_destination field removed from StaticSoundSettings; sounds routed
  to sub-tracks by calling TrackHandle::play() directly instead of
  AudioManager::play()
- set_volume() now accepts f32 (Decibels) not f64
- start_ambient_loop signature updated to take &mut Option<TrackHandle>

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -34,7 +34,7 @@ solitaire_data   = { path = "solitaire_data" }
 solitaire_engine = { path = "solitaire_engine" }
 
 bevy = "0.18"
-kira = "0.9"
+kira = "0.12"
 
 axum               = "0.8"
 sqlx               = { version = "0.8", features = ["runtime-tokio-rustls", "sqlite", "macros", "migrate"] }