feat: plakat redesign phase 1 (tokens, fonts, poster hero, header) (#74)

- New design tokens: signal red, ink and paper as RGB channels; ink and paper
  swap roles in dark mode so every component inverts cleanly
- Fonts via next/font: Bricolage Grotesque (with wdth/opsz axes), Geist,
  Geist Mono; drop Inter and Playfair
- Poster hero: kicker, giant DK0 wordmark that reacts to pointer distance
  (weight and width through a damped spring, desktop only, off for reduced
  motion), claim as h1, intro with thesis countdown, marquee strip
- Header in poster style: transparent over the red hero, paper strip with
  ink rule when scrolled or on subpages; drawer menu restyled
- Remove wavy SVG separators, CSS shader gradient, background blobs and
  unused providers that caused the pink/purple bands between sections
- Drop the global p/span/div color override so colors inherit properly
- New hero texts in de/en, tests and i18n key check updated

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/layout.tsx

@@ -1,24 +1,31 @@
 import "./globals.css";
 import { Metadata } from "next";
-import { Inter, Playfair_Display } from "next/font/google";
+import { Bricolage_Grotesque, Geist, Geist_Mono } from "next/font/google";
 import React from "react";
 import ClientProviders from "./components/ClientProviders";
-import ShaderGradientBackground from "./components/ShaderGradientBackground";
 import { cookies } from "next/headers";
 import { getBaseUrl } from "@/lib/seo";
 
-const inter = Inter({
-  variable: "--font-inter",
+// Bricolage behält die Achsen für Breite und optische Größe, damit das Plakat-Wortbild variieren kann
+const bricolage = Bricolage_Grotesque({
+  variable: "--font-bricolage",
+  subsets: ["latin"],
+  axes: ["opsz", "wdth"],
+  display: "swap",
+  adjustFontFallback: true,
+});
+
+const geist = Geist({
+  variable: "--font-geist",
   subsets: ["latin"],
   display: "swap",
   adjustFontFallback: true,
 });
 
-const playfair = Playfair_Display({
-  variable: "--font-playfair",
+const geistMono = Geist_Mono({
+  variable: "--font-geist-mono",
   subsets: ["latin"],
   display: "swap",
-  adjustFontFallback: true,
 });
 
 export default async function RootLayout({
@@ -37,9 +44,7 @@ export default async function RootLayout({
         {/* Prevent flash of unstyled theme — reads localStorage + system preference before React hydrates */}
         <script dangerouslySetInnerHTML={{ __html: `try{var t=localStorage.getItem('theme');var d=t==='dark'||((!t||t==='system')&&window.matchMedia('(prefers-color-scheme:dark)').matches);if(d)document.documentElement.classList.add('dark');}catch(e){}` }} />
       </head>
-      <body className={`${inter.variable} ${playfair.variable}`} suppressHydrationWarning>
-        <div className="grain-overlay" aria-hidden="true" />
-        <ShaderGradientBackground />
+      <body className={`${bricolage.variable} ${geist.variable} ${geistMono.variable}`} suppressHydrationWarning>
         <ClientProviders>{children}</ClientProviders>
       </body>
     </html>