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/Header.tsx

@@ -1,9 +1,10 @@
 "use client";
 
-import { useState, useEffect } from "react";
+import { useState } from "react";
 import Link from "next/link";
 import { usePathname } from "next/navigation";
-import { DEFAULT_SECTIONS, type SectionConfig } from "@mcpedia/config/sections";
+import { DEFAULT_SECTIONS } from "@mcpedia/config/sections";
+import { useSections } from "@/hooks/useSections";
 import ThemeToggle from "@/components/ThemeToggle";
 import CommandMenu from "@/components/CommandMenu";
 import {
@@ -17,18 +18,8 @@ import {
 export default function Header() {
   const pathname = usePathname();
   const [mobileMenuOpen, setMobileMenuOpen] = useState(false);
-  const [sections, setSections] = useState<SectionConfig[]>(DEFAULT_SECTIONS);
-
-  useEffect(() => {
-    fetch("/api/sections")
-      .then((r) => r.json())
-      .then((data) => {
-        if (Array.isArray(data) && data.length > 0) {
-          setSections(data);
-        }
-      })
-      .catch(() => {});
-  }, []);
+  const { data: liveSections } = useSections();
+  const sections = liveSections && liveSections.length > 0 ? liveSections : DEFAULT_SECTIONS;
 
   return (
     <header className="site-header no-print sticky top-0 z-40 border-b border-[var(--border-color)] glass-nav transition-all">