add CI/CD workflow to build and deploy site to VPS

Builds with slinkity and rsyncs _site/ to /var/www/html/start9.com/ on push to master.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/deploy.yml

@@ -0,0 +1,47 @@
+name: Build and deploy website
+
+on:
+  push:
+    branches: ["master"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: "deploy"
+  cancel-in-progress: false
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build site
+        run: npm run build
+
+      - name: Configure SSH
+        run: |
+          mkdir -p ~/.ssh
+          echo "${{ secrets.DEPLOY_SSH_KEY }}" > ~/.ssh/deploy_key
+          chmod 600 ~/.ssh/deploy_key
+          ssh-keyscan -H start9.com >> ~/.ssh/known_hosts
+          cat >> ~/.ssh/config <<EOF
+          Host website-vps
+            HostName start9.com
+            User root
+            IdentityFile ~/.ssh/deploy_key
+            IdentitiesOnly yes
+          EOF
+
+      - name: Deploy to VPS
+        run: rsync -az --delete _site/ website-vps:/var/www/html/start9.com/