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/useCmsPage.ts

@@ -0,0 +1,29 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+/**
+ * Lädt eine Inhaltsseite (Impressum, Datenschutz) aus dem CMS nach.
+ * Bis dahin und ohne JavaScript bleibt der eingebaute Text stehen.
+ */
+export function useCmsPage(key: string, locale: string): string | null {
+  const [html, setHtml] = useState<string | null>(null);
+
+  useEffect(() => {
+    let cancelled = false;
+    (async () => {
+      try {
+        const res = await fetch(`/api/content/page?key=${encodeURIComponent(key)}&locale=${encodeURIComponent(locale)}`);
+        const data = await res.json();
+        if (!cancelled && data?.content?.html && data?.content?.locale === locale) {
+          setHtml(data.content.html as string);
+        }
+      } catch {}
+    })();
+    return () => {
+      cancelled = true;
+    };
+  }, [key, locale]);
+
+  return html;
+}