Add GitHub Actions Workflow for maintaining & deploying production hosts

The workflow runs on a schedule and can also be triggered manually.

.github/workflows/deploy-production-hosts.yaml

@@ -0,0 +1,24 @@
+name: Maintain & Deploy Production Hosts
+on:
+  schedule:
+    # Run Wednesday and Friday (the days on which I (Julian) usually work) at
+    # 04:00.
+    - cron: "0 4 * * 3,5"
+  workflow_dispatch:
+jobs:
+  Run-Everything-Playbook:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v4
+      - name: Setup .ssh
+        run: |
+          mkdir -p $HOME/.ssh
+          chmod 700 $HOME/.ssh
+          echo "${{ secrets.ANSIBLE_INFRA_SSH_DEPLOY_KEY }}" > $HOME/.ssh/id_ed25519
+          chmod 400 $HOME/.ssh/id_ed25519
+          echo "${{ vars.ANSIBLE_INFRA_SSH_KNOWN_HOSTS }}" > $HOME/.ssh/known_hosts
+      - name: Install dependencies
+        run: ansible-galaxy install -r requirements.yml -f
+      - name: Run playbook
+        run: ansible-playbook -l Production_Hosts playbooks/everything.yaml