perf(theme): make landing animations fully composited

Keep every animation transform/opacity-only so frames never repaint:
- hero ring and loading glow pulse via opacity instead of background-position / box-shadow
- button shine sweeps with transform, not left
- floating glass chips drop animated backdrop-filter (it re-samples every frame)
- promote continuously animated layers (particles, halo, float) with will-change
- drop the negligible blur on moving clouds and remove the unused gradient-shift

src/app/globals.css

@@ -380,7 +380,6 @@ summary,
 	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;
@@ -688,6 +687,7 @@ html.dark .site-backdrop-blob {
 	opacity: 0;
 	animation: particle-rise var(--dot-duration, 12s) linear infinite;
 	animation-delay: var(--dot-delay, 0s);
+	will-change: transform;
 }
 @keyframes particle-rise {
 	0% {
@@ -2055,17 +2055,6 @@ details[open] > summary .details-open\:rotate-180 {
 		opacity: 0.4;
 	}
 }
-@keyframes gradient-shift {
-	0% {
-		background-position: 0% 50%;
-	}
-	50% {
-		background-position: 100% 50%;
-	}
-	100% {
-		background-position: 0% 50%;
-	}
-}
 @keyframes fade-in-up {
 	from {
 		opacity: 0;
@@ -2089,25 +2078,20 @@ details[open] > summary .details-open\:rotate-180 {
 @keyframes pulse-glow {
 	0%,
 	100% {
-		box-shadow: 0 0 8px
-			color-mix(in srgb, var(--color-primary) 25%, transparent);
+		opacity: 0.5;
 	}
 	50% {
-		box-shadow: 0 0 24px
-			color-mix(in srgb, var(--color-primary) 45%, transparent);
+		opacity: 1;
 	}
 }
 
 .animate-float {
 	animation: float 4s ease-in-out infinite;
+	will-change: transform;
 }
 .animate-shimmer {
 	animation: shimmer-glow 2.5s ease-in-out infinite;
 }
-.animate-gradient {
-	background-size: 200% 200%;
-	animation: gradient-shift 8s ease infinite;
-}
 .animate-fade-in-up {
 	animation: fade-in-up 0.6s ease-out both;
 }
@@ -2256,12 +2240,13 @@ details[open] > summary .details-open\:rotate-180 {
 		transparent 65%,
 		transparent 100%
 	);
-	transform: rotate(25deg);
-	transition: all 0.5s ease;
+	transform: translateX(-60%) rotate(25deg);
+	transition: transform 0.6s cubic-bezier(0.33, 1, 0.68, 1);
 	pointer-events: none;
+	will-change: transform;
 }
 .btn-shine:hover::after {
-	left: 100%;
+	transform: translateX(30%) rotate(25deg);
 }
 
 /* Staggered children animation */
@@ -2406,6 +2391,7 @@ html {
 /* Gentle breathing pulse for the brand glows behind Frank / the hero. */
 .brand-halo {
 	animation: hero-halo-pulse 6s ease-in-out infinite;
+	will-change: transform;
 }
 @keyframes hero-halo-pulse {
 	0%,
@@ -2434,7 +2420,8 @@ html {
 }
 
 /* ── Hero pro touches ──────────────────────────────────────────────── */
-/* Continuously shifting gradient hairline drawn on the hero border. */
+/* Continuously shifting gradient hairline drawn on the hero border.
+   Animated with opacity only (fully composited — no per-frame repaint). */
 .hero-ring {
 	position: absolute;
 	inset: 0;
@@ -2448,8 +2435,6 @@ html {
 		color-mix(in srgb, var(--color-accent) 60%, transparent) 65%,
 		color-mix(in srgb, var(--color-primary) 70%, transparent) 100%
 	);
-	background-size: 260% 260%;
-	animation: gradient-shift 14s ease-in-out infinite;
 	-webkit-mask:
 		linear-gradient(#fff 0 0) content-box,
 		linear-gradient(#fff 0 0);
@@ -2459,23 +2444,34 @@ html {
 		linear-gradient(#fff 0 0);
 	mask-composite: exclude;
 	pointer-events: none;
+	animation: hero-ring-pulse 14s ease-in-out infinite;
+}
+@keyframes hero-ring-pulse {
+	0%,
+	100% {
+		opacity: 0.75;
+	}
+	50% {
+		opacity: 1;
+	}
 }
 
-/* Frosted floating stat chips that bob gently on the hero. */
+/* Frosted floating stat chips that bob gently on the hero.
+   No backdrop-filter while animating: sampling the backdrop every frame is
+   expensive, so the chips use a higher-opacity fill instead. */
 .glass-chip {
 	display: inline-flex;
 	align-items: center;
 	gap: 0.45rem;
 	padding: 0.45rem 0.85rem;
 	border-radius: 999px;
-	background: color-mix(in srgb, var(--color-surface) 38%, transparent);
+	background: color-mix(in srgb, var(--color-surface) 72%, transparent);
 	border: 1px solid color-mix(in srgb, var(--color-text-muted) 14%, transparent);
 	box-shadow:
 		0 10px 26px -10px color-mix(in srgb, #000 30%, transparent),
 		inset 0 1px 0 0 color-mix(in srgb, #fff 12%, transparent);
-	backdrop-filter: blur(8px);
-	-webkit-backdrop-filter: blur(8px);
 	animation: float 5s ease-in-out infinite;
+	will-change: transform;
 }
 .glass-chip:nth-child(2) {
 	animation-delay: -1.7s;