fix: Initialize submodules in GitHub Actions workflow

Added submodules: recursive to checkout action to ensure
cms-docs-common submodule is pulled during CI/CD build.

Without this, the config_file reference fails during build.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: andrzejnovak

.github/workflows/deploy-docs.yml

@@ -21,6 +21,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
+        with:
+          submodules: recursive
 
       - name: Setup Python
         uses: actions/setup-python@v5