fix(dock): TRAX ladder gets the mic's ballistics (and a 33 Hz beat)

Reported: the TRAX bar moves, but its sampling looks far slower than the mic meter.

Cause: the TRAX number was a raw instantaneous peak per metering block — a stutter sampled by the UI
timer, with no smoothing. The mic looks fluid because it is smoothed at audio-callback rate.

Fix: the player now smooths its measured level with the SAME curve the mic uses
(MeterScale.NextLevel: fast attack, gentle decay), and the dock's meter clock runs at ~30 Hz instead
of 20. Two ladders that move alike, because they are the same ballistics.

Guard: MeterScaleTests pins the attack/decay behaviour alongside peak-hold.

Services/Audio/MusicPlayer.cs

@@ -84,7 +84,8 @@ public sealed class MusicPlayer : ITraxPlayer
         _volume = new VolumeWaveProvider16(_reader) { Volume = MusicVolume * _userGain * _localGain };
         _metering = new MeteringSampleProvider(_volume.ToSampleProvider());
         _metering.StreamVolume += (_, e) =>
-            Level = e.MaxSampleValues.Length == 0 ? 0f : e.MaxSampleValues.Max();
+            Level = Helpers.MeterScale.NextLevel(Level,
+                e.MaxSampleValues.Length == 0 ? 0f : e.MaxSampleValues.Max());
         _output = new WaveOutEvent();
         _output.PlaybackStopped += OnPlaybackStopped;
         _output.Init(_metering);