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/SearchBar.tsx

@@ -0,0 +1,74 @@
+"use client";
+
+import Link from "next/link";
+import { Search, X } from "lucide-react";
+
+interface SearchBarProps {
+  value: string;
+  onChange: (v: string) => void;
+  placeholder?: string;
+  autoFocus?: boolean;
+  onClear?: () => void;
+}
+
+export default function SearchBar({ value, onChange, placeholder, autoFocus, onClear }: SearchBarProps) {
+  return (
+    <div className="relative">
+      <input
+        type="search"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={placeholder ?? "Search knowledge base..."}
+        autoFocus={autoFocus}
+        className="w-full pl-10 pr-9 py-3 bg-[var(--bg-elevated)] border border-[var(--border-color)] hover:border-[var(--text-muted)] rounded-lg text-[var(--text-primary)] placeholder-[var(--text-dim)] focus:outline-none focus:border-[var(--text-primary)] text-sm transition-all"
+      />
+      <Search className="w-4 h-4 text-[var(--text-muted)] absolute left-3.5 top-3.5 pointer-events-none" />
+      {value && (
+        <button
+          onClick={() => {
+            onChange("");
+            onClear?.();
+          }}
+          className="absolute right-3 top-3 p-0.5 text-[var(--text-dim)] hover:text-[var(--text-primary)] rounded"
+          aria-label="Clear query"
+          type="button"
+        >
+          <X className="w-4 h-4" />
+        </button>
+      )}
+    </div>
+  );
+}
+
+export function InlineSearchBar({
+  value,
+  onChange,
+  placeholder,
+}: {
+  value: string;
+  onChange: (v: string) => void;
+  placeholder?: string;
+}) {
+  return (
+    <div className="relative">
+      <input
+        type="text"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={placeholder ?? "Filter index..."}
+        className="w-full pl-8 pr-7 py-1.5 bg-[var(--bg-surface)] border border-[var(--border-color)] hover:border-[var(--text-muted)] rounded-md text-xs text-[var(--text-primary)] placeholder-[var(--text-dim)] focus:outline-none focus:border-[var(--text-primary)] transition-all"
+      />
+      <Search className="w-3.5 h-3.5 text-[var(--text-dim)] absolute left-2.5 top-2.5 pointer-events-none" />
+      {value && (
+        <button
+          onClick={() => onChange("")}
+          className="absolute right-2 top-2 p-0.5 text-[var(--text-dim)] hover:text-[var(--text-primary)] rounded"
+          aria-label="Clear filter"
+          type="button"
+        >
+          <X className="w-3.5 h-3.5" />
+        </button>
+      )}
+    </div>
+  );
+}