Add Frost feature: implement CSS and JS for frost effects and visibility toggle

Jellyfin.Plugin.Seasonals/Web/frost.js

@@ -0,0 +1,75 @@
+const config = window.SeasonalsPluginConfig?.Frost || {};
+
+const frost = config.EnableFrost !== undefined ? config.EnableFrost : true;
+
+let msgPrinted = false;
+
+function toggleFrost() {
+    const container = document.querySelector('.frost-container');
+    if (!container) return;
+
+    const videoPlayer = document.querySelector('.videoPlayerContainer');
+    const trailerPlayer = document.querySelector('.youtubePlayerContainer');
+    const isDashboard = document.body.classList.contains('dashboardDocument');
+    const hasUserMenu = document.querySelector('#app-user-menu');
+
+    if (videoPlayer || trailerPlayer || isDashboard || hasUserMenu) {
+        container.style.display = 'none';
+        if (!msgPrinted) {
+            console.log('Frost hidden');
+            msgPrinted = true;
+        }
+    } else {
+        container.style.display = 'block';
+        if (msgPrinted) {
+            console.log('Frost visible');
+            msgPrinted = false;
+        }
+    }
+}
+
+const observer = new MutationObserver(toggleFrost);
+observer.observe(document.body, {
+  childList: true,
+  subtree: true,
+  attributes: true
+});
+
+function createFrost(container) {
+    const frostLayer = document.createElement('div');
+    frostLayer.className = 'frost-layer';
+
+    const frostCrystals = document.createElement('div');
+    frostCrystals.className = 'frost-crystals';
+    
+    // An SVG filter to make things look "frozen"/distorted around the edges
+    const svgFilter = document.createElement('div');
+    svgFilter.innerHTML = `
+        <svg style="display:none;">
+            <filter id="frost-filter">
+                <feTurbulence type="fractalNoise" baseFrequency="0.05" numOctaves="3" result="noise" />
+                <feDisplacementMap in="SourceGraphic" in2="noise" scale="5" xChannelSelector="R" yChannelSelector="G" />
+            </filter>
+        </svg>
+    `;
+    
+    frostLayer.appendChild(frostCrystals);
+    container.appendChild(frostLayer);
+    container.appendChild(svgFilter);
+}
+
+function initializeFrost() {
+    if (!frost) return;
+
+    const container = document.querySelector('.frost-container') || document.createElement("div");
+
+    if (!document.querySelector('.frost-container')) {
+        container.className = "frost-container";
+        container.setAttribute("aria-hidden", "true");
+        document.body.appendChild(container);
+    }
+    
+    createFrost(container);
+}
+
+initializeFrost();