feat: plakat redesign for subpages (projects, books, legal, privacy)

- Shared SubpageShell (HeaderClient paper strip + ink footer) and SubpageIntro,
  btn/ghost/card helpers in app/_ui/subpage.tsx
- Projects list: poster cards with hard ink shadows, filter pills, ink search field;
  no fake 800ms skeleton and no framer-motion opacity:0 in SSR
- Project detail: poster hero, .plakat-prose markdown, links/stack aside,
  back link works without JS
- Books: server-side fetch (visible without JS), cover + rating pills
- Legal notice / privacy: moved to app/_ui/*Client.tsx, root routes removed
  (middleware always redirects to /[locale]), consent reset via useConsent
- ProjectThumbnail rebuilt on Plakat tokens
- Old Header.tsx + test removed; brown/cream/sand palettes and unused
  glass-panel/admin-glass(-light)/liquid-bg-blob/float CSS dropped
  (liquid palette, glass-card, admin-glass-card stay for admin + 404)
- .plakat-prose replaces the missing typography plugin

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

app/_ui/subpage.tsx

@@ -0,0 +1,48 @@
+import type { ReactNode } from "react";
+
+// Gemeinsame Bausteine der Unterseiten im Plakat-Stil. Bewusst ohne "use client",
+// damit Server- und Client-Seiten sie gleichermaßen nutzen können.
+
+export const btn =
+  "inline-flex items-center gap-2 rounded-full bg-ink px-5 py-3 text-[15px] font-semibold text-paper transition-transform duration-150 ease-out active:scale-[0.97]";
+
+export const ghost =
+  "inline-flex items-center gap-2 rounded-full px-4 py-2 text-sm font-medium shadow-[inset_0_0_0_1.5px_rgb(var(--plakat-ink))] transition-[background-color,color,transform] duration-150 ease-out hover:bg-ink hover:text-paper active:scale-[0.97]";
+
+/** Rahmen mit hartem Versatzschatten, ohne Hintergrund (für farbige Karten) */
+export const frame = "rounded-[18px] border-2 border-ink shadow-[6px_6px_0_rgb(var(--plakat-ink))]";
+
+export const card = `${frame} bg-paper`;
+
+export const monoLabel = "font-mono text-[13px] leading-snug";
+
+interface SubpageIntroProps {
+  /** Zurück-Link oben links */
+  back: ReactNode;
+  /** Kleine Zeile oben rechts, z. B. Kategorie oder Rechtsgrundlage */
+  kicker?: ReactNode;
+  title: ReactNode;
+  children?: ReactNode;
+}
+
+/** Kopf einer Unterseite: Zurück-Pille, große Plakat-Zeile, Einleitung. */
+export function SubpageIntro({ back, kicker, title, children }: SubpageIntroProps) {
+  return (
+    <header className="border-b-2 border-ink pb-8 md:pb-12">
+      <div className="flex flex-wrap items-center justify-between gap-3">
+        {back}
+        {kicker && <p className={monoLabel}>{kicker}</p>}
+      </div>
+      <h1 className="mt-8 hyphens-auto break-words text-balance font-display text-[clamp(3rem,11vw,9.5rem)] font-extrabold leading-[0.86] tracking-[-0.05em] [font-variation-settings:'wdth'_80] md:mt-12">
+        {title}
+        <span className="text-signal">.</span>
+      </h1>
+      {children && <div className="mt-6 max-w-[52ch] text-lg leading-relaxed md:text-xl">{children}</div>}
+    </header>
+  );
+}
+
+/** Pfeil nach links für Zurück-Links, rein dekorativ */
+export function BackArrow() {
+  return <span aria-hidden="true">←</span>;
+}