feat(auth): bring the landing's cloud sky into login/register

Replace AuthShell's deep-blue grid backdrop with AuthSky — the same bright
pale-blue gradient (weather stop 0) and the same vendored cloud puff
(/cloud.png) as the landing, as lightweight drifting CSS sprites so no
three.js lands on the auth routes. The form keeps the shared frosted-glass
panel, so login/register now read as one world with the public landing.
Cloud drift respects prefers-reduced-motion.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/app/globals.css

@@ -193,8 +193,17 @@ html.lenis body {
 @keyframes abrbanShimmer {
   to { background-position: 200% center; }
 }
+/* Gentle horizontal sway for the auth-screen clouds (see AuthSky). */
+@keyframes abrbanCloudDrift {
+  from { transform: translateX(calc(var(--drift, 6vw) * -1)); }
+  to { transform: translateX(var(--drift, 6vw)); }
+}
 .abrban-float { animation: abrbanFloat 6s ease-in-out infinite; }
 .abrban-scroll-hint { animation: abrbanScrollHint 1.8s ease-in-out infinite; }
+.abrban-cloud-drift {
+  animation: abrbanCloudDrift var(--drift-dur, 40s) ease-in-out infinite alternate;
+  animation-delay: var(--drift-delay, 0s);
+}
 .abrban-shimmer {
   background: linear-gradient(100deg, #93c5fd 0%, #ffffff 25%, #2563eb 50%, #ffffff 75%, #93c5fd 100%);
   background-size: 200% auto;
@@ -223,7 +232,8 @@ html.lenis body {
 @media (prefers-reduced-motion: reduce) {
   .abrban-float,
   .abrban-scroll-hint,
-  .abrban-shimmer {
+  .abrban-shimmer,
+  .abrban-cloud-drift {
     animation: none;
   }
 }

frontend/src/components/auth/AuthShell.tsx

@@ -5,11 +5,12 @@ import { Link } from '@/i18n/Link';
 import { useT } from '@/i18n/I18nProvider';
 import { LanguageSwitcher } from '@/i18n/LanguageSwitcher';
 import { Logo } from '@/components/landing/Logo';
+import { AuthSky } from './AuthSky';
 
-// Auth shell that carries the Abrban brand into a calmer, more premium key: a
-// deep blue gradient, a faint infrastructure grid, soft brand-blue glows and a
-// vignette — no fluffy clouds — with the form inside the same frosted dark-glass
-// panel used across the landing. Direction is inherited from the root layout.
+// Auth shell that carries the Abrban brand straight from the landing: the same
+// bright, cloud-filled sky (see AuthSky) sits behind the form, which lives in the
+// same frosted dark-glass panel — so login/register read as one world with the
+// public landing. Direction is inherited from the root layout.
 export function AuthShell({
   title,
   subtitle,
@@ -27,21 +28,9 @@ export function AuthShell({
 }) {
   const t = useT();
   return (
-    <div className="relative min-h-screen w-full overflow-hidden bg-[#081427] text-white">
-      {/* Background atmosphere */}
-      <div className="pointer-events-none absolute inset-0">
-        {/* Deep brand gradient */}
-        <div className="absolute inset-0 bg-[radial-gradient(125%_120%_at_50%_-10%,#1f5aa0_0%,#0e2c57_45%,#081427_100%)]" />
-        {/* Fine infrastructure grid, faded toward the edges */}
-        <div className="absolute inset-0 opacity-[0.16] [background-image:linear-gradient(rgba(255,255,255,0.10)_1px,transparent_1px),linear-gradient(90deg,rgba(255,255,255,0.10)_1px,transparent_1px)] [background-size:54px_54px] [mask-image:radial-gradient(ellipse_at_center,black_45%,transparent_92%)] [-webkit-mask-image:radial-gradient(ellipse_at_center,black_45%,transparent_92%)]" />
-        {/* Soft brand-blue glows */}
-        <div className="absolute right-[-8%] top-[-12%] h-[30rem] w-[30rem] rounded-full bg-[radial-gradient(circle,_rgba(59,130,246,0.40),_transparent_70%)] blur-3xl" />
-        <div className="absolute bottom-[-14%] left-[-10%] h-[28rem] w-[28rem] rounded-full bg-[radial-gradient(circle,_rgba(37,99,235,0.34),_transparent_70%)] blur-3xl" />
-        {/* Crisp hairline along the very top */}
-        <div className="absolute inset-x-0 top-0 h-px bg-gradient-to-r from-transparent via-white/25 to-transparent" />
-        {/* Vignette to focus the centre */}
-        <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_center,_transparent_55%,_rgba(4,10,22,0.55)_100%)]" />
-      </div>
+    <div className="relative min-h-screen w-full overflow-hidden bg-[#9fb4d4] text-white">
+      {/* Bright cloud-filled sky backdrop, shared with the landing */}
+      <AuthSky />
 
       {/* Header */}
       <header className="relative z-10 mx-auto flex max-w-5xl items-center justify-between px-6 py-5">

frontend/src/components/auth/AuthSky.tsx

@@ -0,0 +1,97 @@
+'use client';
+
+import type { CSSProperties } from 'react';
+
+// A calm, lightweight echo of the landing's cinematic sky — the same pale-blue
+// gradient (weather stop 0) and the very same vendored cloud puff (/cloud.png),
+// but as cheap drifting CSS sprites instead of the full WebGL scene. It keeps the
+// auth screens visually tied to the landing ("ابر" floating behind the form)
+// without pulling three.js onto the login/register routes.
+
+// Each cloud is a small cluster of overlapping puffs so the silhouette reads as a
+// soft fluffy cloud rather than a single blob. Offsets are relative to the
+// cluster's own box (percent of its width).
+const PUFFS = [
+  { l: '0%', t: '32%', w: '52%' },
+  { l: '20%', t: '6%', w: '62%' },
+  { l: '46%', t: '24%', w: '56%' },
+  { l: '28%', t: '40%', w: '66%' },
+];
+
+type CloudSpec = {
+  // Anchor: provide either left/right and either top/bottom.
+  left?: string;
+  right?: string;
+  top?: string;
+  bottom?: string;
+  width: string; // cluster width
+  opacity: number;
+  blur: number; // px
+  drift: string; // horizontal sway amplitude
+  dur: string; // drift duration
+  delay: string; // negative to desync
+};
+
+const CLOUDS: CloudSpec[] = [
+  { top: '6%', left: '-8%', width: '30rem', opacity: 0.92, blur: 1, drift: '7vw', dur: '34s', delay: '0s' },
+  { top: '18%', right: '-10%', width: '36rem', opacity: 0.8, blur: 2, drift: '6vw', dur: '42s', delay: '-7s' },
+  { top: '50%', left: '2%', width: '24rem', opacity: 0.5, blur: 3, drift: '5vw', dur: '38s', delay: '-14s' },
+  { top: '62%', right: '0%', width: '30rem', opacity: 0.58, blur: 3, drift: '8vw', dur: '46s', delay: '-4s' },
+  { bottom: '-6%', left: '18%', width: '38rem', opacity: 0.72, blur: 4, drift: '5vw', dur: '52s', delay: '-22s' },
+];
+
+function Cloud({ spec }: { spec: CloudSpec }) {
+  const driftVars = {
+    '--drift': spec.drift,
+    '--drift-dur': spec.dur,
+    '--drift-delay': spec.delay,
+  } as CSSProperties;
+
+  return (
+    <div
+      className="abrban-cloud-drift pointer-events-none absolute"
+      style={{ left: spec.left, right: spec.right, top: spec.top, bottom: spec.bottom, ...driftVars }}
+    >
+      <div className="abrban-float" style={{ animationDelay: spec.delay }}>
+        <div
+          className="relative"
+          style={{
+            width: spec.width,
+            height: `calc(${spec.width} * 0.6)`,
+            opacity: spec.opacity,
+            filter: `blur(${spec.blur}px)`,
+          }}
+        >
+          {PUFFS.map((p, i) => (
+            <span
+              key={i}
+              className="absolute aspect-square bg-contain bg-center bg-no-repeat"
+              style={{ left: p.l, top: p.t, width: p.w, backgroundImage: 'url(/cloud.png)' }}
+            />
+          ))}
+        </div>
+      </div>
+    </div>
+  );
+}
+
+export function AuthSky() {
+  return (
+    <div className="pointer-events-none absolute inset-0 overflow-hidden">
+      {/* Bright sky gradient — landing weather stop 0 (calm, bright overcast). */}
+      <div className="absolute inset-0 bg-gradient-to-b from-[#9fb4d4] via-[#c3d0e0] to-[#e9f0f8]" />
+      {/* Soft warm sun glow, high and centred, like the landing's hidden sun. */}
+      <div className="absolute left-1/2 top-[-18%] h-[34rem] w-[34rem] -translate-x-1/2 rounded-full bg-[radial-gradient(circle,_rgba(255,242,210,0.55),_transparent_68%)] blur-2xl" />
+      {/* Drifting clouds. */}
+      {CLOUDS.map((spec, i) => (
+        <Cloud key={i} spec={spec} />
+      ))}
+      {/* Low fog haze so the bottom melts into the sky like the landing. */}
+      <div className="absolute inset-x-0 bottom-0 h-1/3 bg-gradient-to-t from-[#e9f0f8]/80 to-transparent" />
+      {/* Crisp hairline along the very top. */}
+      <div className="absolute inset-x-0 top-0 h-px bg-gradient-to-r from-transparent via-white/40 to-transparent" />
+      {/* Vignette to focus the centre — matches LandingPage. */}
+      <div className="absolute inset-0 bg-[radial-gradient(ellipse_at_center,_transparent_62%,_rgba(15,23,42,0.34)_100%)]" />
+    </div>
+  );
+}