Refactor z-index values and optimize CSS properties for various seasonal styles; enhance performance with will-change property [skip ci]

Jellyfin.Plugin.Seasonals/Web/sports.css

@@ -5,16 +5,17 @@
     width: 100vw;
     height: 100vh;
     pointer-events: none;
-    z-index: 9999;
+    z-index: 10;
     overflow: hidden;
     contain: strict;
 }
 
 .sports-symbol {
     position: absolute;
-    top: -10vh;
+    top: 0;
     opacity: 0.9;
     z-index: 40;
+    translate: 0 -10vh;
 }
 
 .sports-inner {
@@ -29,13 +30,15 @@
 }
 
 .sports-confetti {
+    will-change: transform, opacity;
     position: absolute;
-    top: -5vh;
+    top: 0;
     width: 10px;
     height: 15px;
     opacity: 0.8;
     animation: sports-confetti-fall linear infinite;
     border-radius: 2px;
+    translate: 0 -5vh;
 }
 
 .sports-confetti.circle {