fix: solid cover-color NP background via canvas extraction

Replace saturated blur filter with actual dominant-color extraction:
fetch cover as blob (avoids canvas CORS taint), draw on 24x24 canvas,
find most vivid pixel, darken to ~28% for a moody solid background.
Blurred bg layers hidden when mode is active. Transitions smoothly
between songs via CSS transition on background.
Renamed setting label to "Einfarbiger Player-Hintergrund".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

styles.css

@@ -590,10 +590,9 @@ button:focus{outline:none}
   will-change:opacity;
   z-index:0;
 }
-/* Dynamic cover color mode: more vivid/saturated background */
-.np-overlay.dynamic-color .np-bg{
-  filter:blur(60px) brightness(.5) saturate(3);
-}
+/* Solid cover-color mode: hide blurred layers, use extracted color as background */
+.np-overlay.dynamic-color{background:rgb(var(--np-solid,20,20,40));transition:background .5s ease,transform .35s cubic-bezier(.4,0,.2,1)}
+.np-overlay.dynamic-color .np-bg{opacity:0!important;pointer-events:none}
 
 .np-inner{
   position:relative;z-index:1;