Update deploy action to not trigger on pull requests

.github/workflows/deploy.yml

@@ -0,0 +1,39 @@
+name: Deploy app to server
+
+on:
+  workflow_run:
+    workflows: [ 'Playwright tests' ]
+    types: [ completed ]
+    branches: [ devel, main ]
+env:
+  SERVER_USER: root
+  SERVER_IP: 128.140.75.240
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    if: |
+      github.event.workflow_run.conclusion == 'success' &&
+      github.event.workflow_run.event == 'push'
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install Nix
+      uses: cachix/install-nix-action@v27
+      with:
+        github_access_token: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Install SSH Key
+      uses: shimataro/ssh-key-action@v2
+      with:
+        key: ${{ secrets.DEMO_SERVER_SSH_KEY }}
+        known_hosts: ${{ secrets.DEMO_SERVER_KNOWN_HOSTS }}
+
+    - name: Deploy to demo server
+      run: |
+        nix run nixpkgs#nixos-rebuild -- switch \
+          --flake .#demo-server \
+          --fast \
+          --build-host ${{ env.SERVER_USER }}@${{ env.SERVER_IP }} \
+          --target-host ${{ env.SERVER_USER }}@${{ env.SERVER_IP }} \
+          --use-remote-sudo