revert(android): drop NowPlaying scrubber height clamp

Operator: the slider height clamp shifted the surrounding layout
above and below — not what they intended to change. Revert the
Modifier.height(20.dp) and remove the SCRUB_SLIDER_HEIGHT_DP
constant; the Slider goes back to its M3-default 48dp interactive
component height so adjacent rows sit where they did before.

The slim 4dp custom track stays — that's what addresses the
"puffy bar" feel — and the thumb still sits on it as a visible
14dp circle, with 17dp empty vertical space above and below.
That's the M3 standard layout the operator wants restored.

android/app/src/main/java/com/fabledsword/minstrel/player/ui/NowPlayingScreen.kt

@@ -88,7 +88,6 @@ private const val PLAY_PAUSE_ICON_DP = 56
 private const val POP_GRACE_MS = 500L
 private val SCRUB_TRACK_HEIGHT_DP = 4.dp
 private val SCRUB_TRACK_CORNER_DP = 2.dp
-private val SCRUB_SLIDER_HEIGHT_DP = 20.dp
 
 // Vertical drag-down threshold (in pixels) past which the gesture
 // pops the player. Matches Flutter's 80px threshold in spirit;
@@ -476,12 +475,7 @@ private fun ScrubberRow(positionMs: Long, durationMs: Long, onSeek: (Long) -> Un
         onValueChange = { newFraction ->
             if (durationMs > 0) onSeek((newFraction * durationMs).toLong())
         },
-        // Clamp the Slider's vertical footprint so the M3-default
-        // 48dp interactive-component padding doesn't leave the thumb
-        // floating in empty space above and below the track. 20dp =
-        // 14dp thumb + 3dp clearance each side; touch area is still
-        // wide enough since the drag axis is horizontal.
-        modifier = Modifier.fillMaxWidth().height(SCRUB_SLIDER_HEIGHT_DP),
+        modifier = Modifier.fillMaxWidth(),
         colors = sliderColors,
         interactionSource = interactionSource,
         // Plain filled circle to match the web client's `<input