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>

readme.md

@@ -93,6 +93,35 @@ gpg --homedir ~/.gnupg/lair --quick-add-key <master-fpr> ed25519 sign 1y
 
 Then update the `RPM_SIGNING_KEY` secret in Gitea with the new subkey. The public key served to users doesn't change since it's anchored to the master key.
 
+### 5. Runner prerequisites
+
+#### nvm (for UI builds)
+
+Runners that build the UI need [nvm](https://github.com/nvm-sh/nvm) installed for the `gitea_runner` user and an `nvm` label in their runner config:
+
+```bash
+sudo -u gitea_runner bash -c 'curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash'
+```
+
+Then add `nvm` to the labels in `/etc/act_runner/config.yml`:
+
+```yaml
+runner:
+  labels:
+    - "fedora-43:host"
+    - "nvm"
+```
+
+Restart the runner after changing labels. The `deploy-ui` workflow uses `runs-on: [fedora-43, nvm]` to select runners with Node.js capability.
+
+#### sequoia-sq (for RPM signing)
+
+Runners that run the publish job need `sequoia-sq` installed:
+
+```bash
+sudo dnf install sequoia-sq
+```
+
 ## Client setup
 
 ```bash