tweak: sun stripes use semi-transparent purple instead of solid black

rgba(20,0,50,0.72) lets the gradient bleed through the bands, reducing
harsh contrast while keeping the stripe effect visible.

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

plugin/contents/ui/dancer.html

@@ -738,10 +738,10 @@ html, body {
   background:
     repeating-linear-gradient(
       to bottom,
-      transparent    0px,
-      transparent   13px,
-      #000814       13px,
-      #000814       17px
+      transparent          0px,
+      transparent         13px,
+      rgba(20, 0, 50, 0.72) 13px,
+      rgba(20, 0, 50, 0.72) 17px
     ),
     linear-gradient(to bottom,
       #fff9cc  0%,