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/SubpageShell.tsx

@@ -0,0 +1,27 @@
+import type { ReactNode } from "react";
+import Header from "../components/Header.server";
+import { FooterClient } from "../components/ClientWrappers";
+import { getFooterTranslations } from "@/lib/translations-loader";
+
+interface SubpageShellProps {
+  locale: string;
+  children: ReactNode;
+}
+
+/**
+ * Rahmen für alle Unterseiten: derselbe Kopf wie auf der Startseite
+ * (dort als Papierstreifen), Papier als Grund, Tinten-Footer.
+ */
+export default async function SubpageShell({ locale, children }: SubpageShellProps) {
+  const footerT = await getFooterTranslations(locale);
+
+  return (
+    <div id="top" className="min-h-screen bg-paper text-ink">
+      <Header locale={locale} />
+      <main className="px-4 pb-20 pt-24 sm:px-6 md:pb-28 md:pt-32 lg:px-10">
+        <div className="mx-auto max-w-[1400px]">{children}</div>
+      </main>
+      <FooterClient locale={locale} translations={footerT} />
+    </div>
+  );
+}