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

Jellyfin.Plugin.Seasonals/Web/spring.css

@@ -29,13 +29,14 @@
 /* Sunbeams */
 .spring-sunbeam {
     position: fixed;
-    top: -50%;
+    top: 0;
     height: 200%;
     background: linear-gradient(to bottom, rgba(255, 255, 255, 0), rgba(255, 255, 200, 0.08) 50%, rgba(255, 255, 255, 0));
     z-index: 5; 
     transform-origin: top center;
     pointer-events: none;
     opacity: 0; 
+    translate: 0 -50vh;
 }
 
 /* Grass Container (Wrapper) */
@@ -72,6 +73,7 @@
 
 /* SVG Meadow Layer */
 .spring-meadow-layer {
+    will-change: transform;
     position: absolute;
     bottom: 0;
     left: 0;
@@ -94,6 +96,7 @@
 }
 
 .spring-sway {
+    will-change: transform;
     transform-origin: bottom center;
     animation: spring-meadow-sway 4s ease-in-out infinite alternate;
 }