fix(android): always use dominant swatch for NowPlaying background

Operator framing: the cover art is the main feature of NowPlaying,
not the background. A vibrant accent on the cover (small bright
logo, sticker, stripe) should pop against the background, not be
matched by it. The previous vibrant → muted → dominant fallback
chain often picked a high-saturation accent that covered only a
sliver of the cover, producing gradients that clashed with the
actual image.

Drop to dominantSwatch only — the majority-by-pixel-count color.
If the palette resolves no dominant swatch (extremely rare;
essentially uniform/empty bitmap) the held color stays on the
previous track's dominant, matching the existing "keep previous
on failure" docstring contract.

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

@@ -59,9 +59,14 @@ fun rememberDominantColor(coverUrl: String?): Color {
         val palette = withContext(Dispatchers.Default) {
             Palette.from(bitmap).generate()
         }
-        val swatch = palette.vibrantSwatch
-            ?: palette.mutedSwatch
-            ?: palette.dominantSwatch
+        // Always use the dominant (majority-by-pixel-count) swatch.
+        // The cover art is the main feature of this view; a vibrant
+        // accent on the cover should pop against the background, not
+        // be matched by it. Previously we tried vibrant first, which
+        // picked the highest-saturation swatch even when it covered
+        // a tiny fraction of the cover — small bright accents made
+        // the gradient feel disconnected from the actual image.
+        val swatch = palette.dominantSwatch
         if (swatch != null) {
             extracted = Color(swatch.rgb)
         }