feat: add React UI for rpm.lair.cafe

- Vite + React + SWC + TypeScript SPA with react-router and
  react-bootstrap
- Dark/light/system theme with Bootstrap 5.3 data-bs-theme
- Home page with repo setup instructions and copyable code blocks
- Package list and detail pages driven by packages.json
- Python script to generate packages.json from repodata XML
- Nginx config updated for SPA fallback, asset caching, removed
  autoindex
- New deploy-ui workflow triggered on ui/ or nginx config changes,
  requires runners with nvm label
- packages.json generation added to publish job after createrepo_c
- Runner setup docs for nvm and sequoia-sq added to readme

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/hooks/usePackages.ts

@@ -0,0 +1,36 @@
+import { useEffect, useState } from "react";
+import type { PackagesManifest } from "../types/packages.ts";
+
+const MANIFEST_URL = "/fedora/43/x86_64/packages.json";
+
+export function usePackages() {
+  const [manifest, setManifest] = useState<PackagesManifest | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    let cancelled = false;
+
+    fetch(MANIFEST_URL)
+      .then((res) => {
+        if (!res.ok) throw new Error(`HTTP ${res.status}`);
+        return res.json() as Promise<PackagesManifest>;
+      })
+      .then((data) => {
+        if (!cancelled) setManifest(data);
+      })
+      .catch((err: unknown) => {
+        if (!cancelled)
+          setError(err instanceof Error ? err.message : String(err));
+      })
+      .finally(() => {
+        if (!cancelled) setLoading(false);
+      });
+
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
+  return { manifest, loading, error };
+}