chore(.github/workflows): add system dependencies for pycairo

Add libcairo2-dev and pkg-config to the dependency-audit.yml workflow so that pycairo can be installed correctly on CI runners. This prevents the build error when installing Python packages that require the Cairo library.

.github/workflows/dependency-audit.yml

@@ -22,6 +22,9 @@ jobs:
         with:
           python-version: "3.13"
 
+      - name: Install system deps for pycairo
+        run: sudo apt-get install -y libcairo2-dev pkg-config
+
       - name: Install uv
         uses: astral-sh/setup-uv@v4