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/api/docs/route.ts

@@ -78,8 +78,15 @@ function splitPayload(body: Record<string, unknown>): {
 }
 
 // GET /api/docs — list all documents (for sidebar navigation).
-export async function GET() {
-  const docs = await listDocuments();
+// Supports ?section=&status= filters.
+export async function GET(req: NextRequest) {
+  const { searchParams } = new URL(req.url);
+  const section = searchParams.get("section") ?? undefined;
+  const status = searchParams.get("status") ?? undefined;
+  const docs = await listDocuments({
+    ...(section ? { section } : {}),
+    ...(status ? { status } : {}),
+  });
   return NextResponse.json(docs);
 }