feat: redesign auth pages — rounded-[48px] cards, serif titles, orbs, icon inputs

- Auth layout: warm background with brand-accent/ochre orbs, header with Globe + Momento branding
- Login form: serif heading, icon-inputs with focus transitions, uppercase labels, submit with arrow
- Register form: matching card style with User/Mail/Lock icons, confirm password field
- Forgot password: matching card with email icon, success state with mail icon
- Reset password: matching card with Lock icons, invalid link state with AlertCircle
- All text via i18n (new keys: welcomeBack, createYourSpace, forgot, etc.)
- Dark mode support via CSS variables
- Removed shadcn Card/Button/Input dependencies from auth forms

memento-note/app/(auth)/layout.tsx

@@ -1,6 +1,8 @@
 'use client';
 
 import { LanguageProvider } from '@/lib/i18n/LanguageProvider';
+import Link from 'next/link';
+import { Globe } from 'lucide-react';
 
 export default function AuthLayout({
   children,
@@ -9,10 +11,38 @@ export default function AuthLayout({
 }>) {
   return (
     <LanguageProvider>
-      <div className="flex min-h-screen items-center justify-center bg-gray-50 dark:bg-zinc-950">
-        <div className="w-full max-w-md p-4">
-          {children}
-        </div>
+      <div className="min-h-screen bg-[#FDFCFB] dark:bg-[#0D0D0D] flex flex-col relative overflow-hidden">
+        <div className="absolute top-[-10%] right-[-10%] w-[50%] h-[50%] bg-[var(--color-brand-accent)]/5 blur-[120px] rounded-full pointer-events-none" />
+        <div className="absolute bottom-[-10%] left-[-10%] w-[50%] h-[50%] bg-[#D4A373]/5 blur-[120px] rounded-full pointer-events-none" />
+
+        <header className="p-6 md:p-8 flex justify-between items-center relative z-10">
+          <Link
+            href="/"
+            className="flex items-center gap-2 text-[var(--muted-foreground)] hover:text-[var(--foreground)] transition-colors group"
+          >
+            <div className="w-8 h-8 rounded-full border border-[var(--border)] flex items-center justify-center group-hover:border-[var(--color-brand-accent)] transition-colors">
+              <Globe size={14} className="group-hover:rotate-12 transition-transform" />
+            </div>
+          </Link>
+
+          <Link href="/" className="flex items-center gap-2">
+            <div className="w-8 h-8 bg-[var(--foreground)] text-[var(--background)] rounded-xl flex items-center justify-center shadow-lg">
+              <span className="font-serif font-bold text-xl">M</span>
+            </div>
+            <span className="font-serif text-xl font-medium tracking-tight">Momento</span>
+          </Link>
+
+          <div className="w-8" />
+        </header>
+
+        <main className="flex-1 flex items-center justify-center p-4 md:p-6 relative z-10">
+          <div className="w-full max-w-md">
+            {children}
+            <p className="text-center mt-8 text-[9px] text-[var(--muted-foreground)] font-bold uppercase tracking-[0.3em] opacity-40 select-none">
+              © 2025 Momento Labs
+            </p>
+          </div>
+        </main>
       </div>
     </LanguageProvider>
   );