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/[locale]/projects/page.tsx

@@ -1,5 +1,6 @@
 import { prisma } from "@/lib/prisma";
 import ProjectsPageClient, { ProjectListItem } from "@/app/_ui/ProjectsPageClient";
+import SubpageShell from "@/app/_ui/SubpageShell";
 import type { Metadata } from "next";
 import { getLanguageAlternates, toAbsoluteUrl } from "@/lib/seo";
 import { getProjects as getDirectusProjects } from "@/lib/directus";
@@ -94,6 +95,10 @@ export default async function ProjectsPage({
     return dateB - dateA;
   });
 
-  return <ProjectsPageClient projects={allProjects} locale={locale} />;
+  return (
+    <SubpageShell locale={locale}>
+      <ProjectsPageClient projects={allProjects} locale={locale} />
+    </SubpageShell>
+  );
 }