feat(site): drifting cloud puffs across the public background

Add a fixed, decorative layer of soft clouds that slowly float across
the Habbo sky behind the content:
- Five clouds at staggered sizes, heights, opacities and loop timings
  (60s–190s) so the drift feels organic.
- Dimmed further in dark mode; frozen by prefers-reduced-motion.
- Pure decoration: aria-hidden, pointer-events: none, no color
  utilities in markup (cloud shapes live in globals.css).

src/app/globals.css

@@ -342,6 +342,97 @@ summary,
 			transparent 100%
 		);
 }
+/* Floating cloud puffs drifting across the public background. */
+.clouds {
+	position: fixed;
+	inset: 0;
+	z-index: -1;
+	pointer-events: none;
+	overflow: hidden;
+}
+.cloud {
+	position: absolute;
+	width: clamp(140px, 22vw, 260px);
+	height: clamp(40px, 7vw, 70px);
+	left: 0;
+	opacity: 0.7;
+	transform: scale(var(--cloud-scale, 1));
+	filter: blur(0.5px);
+	will-change: transform;
+	animation-name: cloud-drift;
+	animation-timing-function: linear;
+	animation-iteration-count: infinite;
+	background:
+		radial-gradient(
+			ellipse 62% 55% at 30% 50%,
+			rgba(255, 255, 255, 0.6) 0%,
+			transparent 70%
+		),
+		radial-gradient(
+			ellipse 70% 60% at 55% 45%,
+			rgba(255, 255, 255, 0.55) 0%,
+			transparent 72%
+		),
+		radial-gradient(
+			ellipse 60% 55% at 78% 58%,
+			rgba(255, 255, 255, 0.45) 0%,
+			transparent 72%
+		);
+}
+.cloud-1 {
+	--cloud-scale: 1.15;
+	top: 7%;
+	animation-duration: 95s;
+	animation-delay: -30s;
+}
+.cloud-2 {
+	--cloud-scale: 0.75;
+	top: 15%;
+	opacity: 0.45;
+	animation-duration: 130s;
+	animation-delay: -85s;
+}
+.cloud-3 {
+	--cloud-scale: 0.9;
+	top: 24%;
+	opacity: 0.5;
+	animation-duration: 160s;
+	animation-delay: -60s;
+}
+.cloud-4 {
+	--cloud-scale: 0.6;
+	top: 34%;
+	opacity: 0.3;
+	animation-duration: 110s;
+	animation-delay: -105s;
+}
+.cloud-5 {
+	--cloud-scale: 1.35;
+	top: 45%;
+	opacity: 0.22;
+	animation-duration: 190s;
+	animation-delay: -140s;
+}
+@keyframes cloud-drift {
+	0% {
+		transform: translateX(clamp(-30vw, -220px, -140px))
+			scale(var(--cloud-scale, 1));
+	}
+	100% {
+		transform: translateX(calc(100vw + 260px)) scale(var(--cloud-scale, 1));
+	}
+}
+html.dark .cloud {
+	opacity: 0.28;
+}
+@media (prefers-reduced-motion: reduce) {
+	.cloud {
+		animation: none;
+		transform: translateX(clamp(-30vw, -220px, -140px))
+			scale(var(--cloud-scale, 1));
+	}
+}
+
 /* Subtle primary glow */
 .site-bg::after {
 	content: "";