feat(web): privacy-first cookie banner

- New CookieBanner client component anchored at the bottom of the locale
  layout, dismissed via Button click and persisted via localStorage key
  ketopath:cookie-notice-ack (no cookie set for the dismissal itself)
- Italian copy: only essential cookies for authentication/session, no
  analytics or third-party trackers (consistent with the ADR 0001 stance
  and CLAUDE.md "Privacy first" non-negotiable)
- Layout body now uses bg-background / text-foreground tokens so dark mode
  toggling will work the day we add it

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/app/[locale]/layout.tsx

@@ -5,6 +5,7 @@ import { NextIntlClientProvider } from 'next-intl';
 import { getMessages, getTranslations, setRequestLocale } from 'next-intl/server';
 import type { ReactNode } from 'react';
 
+import { CookieBanner } from '@/components/cookie-banner';
 import { locales, type Locale } from '@/i18n';
 
 import '@/styles/globals.css';
@@ -48,9 +49,10 @@ export default async function LocaleLayout({
 
   return (
     <html lang={locale} className={inter.variable}>
-      <body className="min-h-screen bg-white font-sans text-slate-900 antialiased">
+      <body className="bg-background text-foreground min-h-screen font-sans antialiased">
         <NextIntlClientProvider locale={locale} messages={messages}>
           {children}
+          <CookieBanner />
         </NextIntlClientProvider>
       </body>
     </html>