Add Film Noir feature: implement CSS and JS for film noir effects and toggle functionality

Jellyfin.Plugin.Seasonals/Web/filmnoir.css

@@ -0,0 +1,86 @@
+.filmnoir-tint {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100vw;
+    height: 100vh;
+    pointer-events: none;
+    z-index: 10000;
+    background-color: #8c7355;
+    mix-blend-mode: color;
+}
+
+.filmnoir-effects {
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100vw;
+    height: 100vh;
+    pointer-events: none;
+    z-index: 1100;
+}
+
+/* Film grain */
+.filmnoir-grain {
+    position: absolute;
+    top: -50%;
+    left: -50%;
+    width: 200%;
+    height: 200%;
+    background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200"><filter id="n"><feTurbulence type="fractalNoise" baseFrequency="0.8" numOctaves="3" stitchTiles="stitch"/></filter><rect width="200" height="200" filter="url(%23n)" opacity="0.4"/></svg>');
+    animation: grain-dance 0.2s steps(4) infinite;
+    pointer-events: none;
+    mix-blend-mode: overlay;
+    opacity: 0.3;
+}
+
+/* Vignette */
+.filmnoir-vignette {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    pointer-events: none;
+    background: radial-gradient(circle at center, transparent 50%, rgba(0,0,0,0.8) 120%);
+    box-shadow: inset 0 0 100px rgba(0,0,0,0.6);
+}
+
+/* Occasional flicker and scratch */
+.filmnoir-scratches {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    pointer-events: none;
+    background: linear-gradient(to right, transparent 50%, rgba(255,255,255,0.2) 51%, transparent 52%);
+    background-size: 200% 100%;
+    animation: scratch 4s infinite linear, flicker 6s infinite alternate;
+    opacity: 0.2;
+    mix-blend-mode: screen;
+}
+
+@keyframes grain-dance {
+    0% { transform: translate(0,0); }
+    25% { transform: translate(-5%,-5%); }
+    50% { transform: translate(-10%,5%); }
+    75% { transform: translate(5%,-10%); }
+    100% { transform: translate(0,0); }
+}
+
+@keyframes scratch {
+    0% { background-position: -200% 0; }
+    10% { background-position: 200% 0; }
+    100% { background-position: 200% 0; }
+}
+
+@keyframes flicker {
+    0% { opacity: 0.2; }
+    5% { opacity: 0.1; }
+    10% { opacity: 0.3; }
+    15% { opacity: 0.2; }
+    50% { opacity: 0.15; }
+    55% { opacity: 0.25; }
+    100% { opacity: 0.2; }
+}