feat(public): add Theater Mode to release detail pages

Toggle left of the lava popover hides release content so the visualizer fills
the surface; player bar grows to carry the playing release's cover, title, and
share. State on WaveformVisualizerControlState; pages and bar observe it.

DeepDrftPublic.Client/Controls/AudioPlayerBar/AudioPlayerBar.razor

@@ -10,6 +10,15 @@ else
         <MudContainer MaxWidth="MaxWidth.Large" Class="player-inner-container">
             <MudPaper Elevation="8" Class="player-surface pa-3">
 
+                @* Theater Mode "now showing" band (Phase 20 §5/§7). Shown only when Theater is ON and a
+                   release is playing — keyed off the playing track's Release, not off any detail page
+                   (the bar reaches into no page; §6). The release page is hidden in Theater Mode, so the
+                   bar carries its identity: cover, linked title, release share. *@
+                @if (VisualizerControlState.TheaterMode && CurrentTrack?.Release is not null)
+                {
+                    <NowShowingPanel Release="CurrentTrack.Release" />
+                }
+
                 <div class="player-layout">
                     <PlayerTransportZone IsLoaded="IsLoaded"
                                          CanPlay="CanPlay"