Ensure package-lock.json exists in deploy workflow

Added a step to ensure package-lock.json exists before installing dependencies.

Author: Diana-Cl

.github/workflows/deploy.yml

@@ -32,8 +32,15 @@ jobs:
       - name: Setup Pages
         uses: actions/configure-pages@v4
 
+      - name: Ensure lock file exists
+        run: |
+          if [ ! -f package-lock.json ]; then
+            echo "Error: package-lock.json is missing. Run 'npm install' locally and commit the generated lock file."
+            exit 1
+          fi
+
       - name: Install dependencies
-        run: npm install
+        run: npm ci
 
       - name: Build with VitePress
         run: npm run build