use new vars and envs for deploy action

.github/workflows/deploy.yml

@@ -15,10 +15,14 @@ jobs:
           install -m 600 -D /dev/null ~/.ssh/id_ed25519
           echo "${{ secrets.SSH_PRIVATE_KEY }}" > ~/.ssh/id_ed25519
           chmod 600 ~/.ssh/id_ed25519  # This should be redundant but seems to do the trick.
-          ssh-keyscan -H ${{ secrets.SSH_HOST }} > ~/.ssh/known_hosts
+          ssh-keyscan -H ${{ vars.SSH_HOST }} > ~/.ssh/known_hosts
 
       - name: Connect, pull, build and deploy
-        run: ssh ${{ secrets.SSH_USER }}@${{ secrets.SSH_HOST }} "cd ${{ secrets.WORK_DIR }} && git checkout ${{ secrets.MAIN_BRANCH }} && git pull && docker compose down && docker compose up -d --build && exit"
+        run: ssh ${{ secrets.SSH_USER }}@${{ vars.SSH_HOST }} "cd ${{ secrets.WORK_DIR }} && git checkout ${{ vars.MAIN_BRANCH }} && git pull && docker compose down && docker compose up -d --build && exit"
 
       - name: Clean up
         run: rm -rf ~/.ssh
+
+    permissions:
+      contents: read
+      pull-requests: write