feat(web): FE overhaul — SWR centralized data layer + dashboard + islands

- Add SWR foundation (lib/fetcher, lib/swr, lib/api) with typed
  hooks: useSections/useDocuments/useSearch/useRelated/useRevisions/useQueueStatus
- Replace ad-hoc useEffect+fetch in Header/Sidebar/CommandMenu/search
  with SWR (dedup 4s, focus throttle 10s, debounced search 180ms)
- Doc page: RelatedGrid + RevisionList as SWR client islands (RSC hero stays)
- DocForm: SWR mutate on create/update for live sidebar invalidation
- New APIs: /api/related, /api/revisions, /api/tags, /api/queue/status,
  /api/docs filtering (?section=&status=)
- New UI: DocumentCard, SectionCard, SearchBar, TagCloud, QueueBadge,
  EmptyState, dashboard (/dashboard with QueueStrip live + section stats)
- Layout wraps SWRProvider; no TanStack code (SWR-only per spec)
- Verified: next build passes (16.3.4 Turbopack), no manual fetch sprawl remains

Co-Authored-By: internal-model

apps/web/app/components/SectionCard.tsx

@@ -0,0 +1,36 @@
+import Link from "next/link";
+
+export function SectionCard({
+  id,
+  label,
+  icon,
+  desc,
+  docCount,
+}: {
+  id: string;
+  label: string;
+  icon: string;
+  desc: string;
+  docCount: number;
+}) {
+  return (
+    <div className="group flex flex-col justify-between bg-[var(--bg-surface)] hover:bg-[var(--bg-surface-hover)] border border-[var(--border-color)] hover:border-[var(--text-muted)] rounded-xl p-5 transition-all shadow-xs">
+      <div>
+        <div className="flex items-center justify-between gap-2 mb-3">
+          <span className="text-2xl">{icon}</span>
+          <Link
+            href={`/${id}`}
+            className="text-xs font-mono text-[var(--text-muted)] hover:text-[var(--text-primary)] font-semibold"
+          >
+            {docCount} docs →
+          </Link>
+        </div>
+        <h3 className="font-bold text-sm text-[var(--text-primary)] mb-1">{label}</h3>
+        <p className="text-xs text-[var(--text-muted)] mb-4 line-clamp-2 leading-relaxed">{desc}</p>
+      </div>
+      <div className="pt-3 border-t border-[var(--border-color)] text-xs text-[var(--text-dim)] font-mono">
+        /{id} · {docCount} document{docCount !== 1 ? "s" : ""}
+      </div>
+    </div>
+  );
+}