Add seasonal themes for Birthday, Olympia, Space, Sports, and Underwater: implement CSS and JavaScript for visual effects and configurations

Jellyfin.Plugin.Seasonals/Web/space.css

@@ -0,0 +1,58 @@
+.space-container {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100vw;
+    height: 100vh;
+    pointer-events: none;
+    z-index: 9999;
+    overflow: hidden;
+    contain: strict;
+}
+
+.space-symbol {
+    position: absolute;
+    animation-timing-function: linear;
+    animation-iteration-count: infinite;
+    font-size: 3rem;
+    opacity: 0.85;
+    z-index: 9999;
+}
+
+.space-symbol img {
+    width: 6vh;
+    height: auto;
+    max-width: 60px;
+    object-fit: contain;
+    /* Add a slow spin to images */
+    animation: space-slow-spin var(--rot-dur, 20s) linear infinite;
+}
+
+/* Specific elements scaling */
+.space-planet1, .space-planet2 { font-size: 4rem; }
+.space-planet1 img, .space-planet2 img { width: 8vh; max-width: 80px; }
+.space-star { font-size: 2rem; opacity: 0.6; }
+.space-star img { width: 3vh; max-width: 30px; }
+
+@keyframes space-drift-right {
+    0% {
+        transform: translateX(0) scaleX(-1);
+    }
+    100% {
+        transform: translateX(120vw) scaleX(-1);
+    }
+}
+
+@keyframes space-drift-left {
+    0% {
+        transform: translateX(0);
+    }
+    100% {
+        transform: translateX(-120vw);
+    }
+}
+
+@keyframes space-slow-spin {
+    0% { transform: rotate(0deg); }
+    100% { transform: rotate(360deg); }
+}