Replace MudSlider seekbar with WaveformSeeker loudness-waveform control

DOM bar chart with clip-overlay progress split; pointer-capture drag;
WaveformProfile fetched on load (fire-and-forget, cancellable); flat
fallback when no profile; small lazily-loaded waveformSeeker.js for
getBoundingClientRect and setPointerCapture.

DeepDrftPublic.Client/Controls/AudioPlayerBar/PlayerSeekZone.razor.cs

@@ -3,48 +3,17 @@ using Microsoft.AspNetCore.Components;
 namespace DeepDrftPublic.Client.Controls.AudioPlayerBar;
 
 /// <summary>
-/// Centre zone of the player: seek slider over the spectrum visualizer.
-/// Owns the pointer-gesture seek logic (drag-to-seek) in one place so it is no
-/// longer duplicated inline between the desktop and mobile branches of the parent.
+/// Centre zone of the player: the <see cref="WaveformSeeker"/> over a timestamp label.
+/// The seeker owns the pointer-gesture seek logic and reads playback state off the cascaded
+/// player service directly; this zone just forwards the seek callbacks up to
+/// <see cref="AudioPlayerBar"/> (whose wiring is unchanged) and renders the timestamp.
 /// </summary>
 public partial class PlayerSeekZone : ComponentBase
 {
-    private double _seekPosition;
-    private bool _isSeeking = false;
-
     [Parameter] public double DisplayTime { get; set; }
     [Parameter] public double? Duration { get; set; }
-    [Parameter] public bool CanSeek { get; set; }
     [Parameter] public EventCallback OnSeekStart { get; set; }
     [Parameter] public EventCallback<double> OnSeekEnd { get; set; }
     [Parameter] public EventCallback<double> OnSeekChange { get; set; }
     [Parameter] public string? Class { get; set; }
-
-    private async Task HandlePointerDown()
-    {
-        _isSeeking = true;
-        _seekPosition = DisplayTime;
-        await OnSeekStart.InvokeAsync();
-    }
-
-    private async Task HandlePointerUp()
-    {
-        _isSeeking = false;
-        await OnSeekEnd.InvokeAsync(_seekPosition);
-    }
-
-    private async Task HandlePointerLeave()
-    {
-        if (_isSeeking)
-        {
-            _isSeeking = false;
-            await OnSeekEnd.InvokeAsync(_seekPosition);
-        }
-    }
-
-    private async Task HandleValueChanged(double value)
-    {
-        _seekPosition = value;
-        await OnSeekChange.InvokeAsync(value);
-    }
 }