ci: install libatomic1 for backend pyright runtime

.gitea/workflows/cicd-source-checks.yaml

@@ -206,6 +206,8 @@ jobs:
             tar -xzf - -C /workspace
             cd /workspace/backend
             test -f pyproject.toml
+            apt-get update -qq
+            apt-get install -y -qq --no-install-recommends libatomic1
             python -m pip install --disable-pip-version-check --no-cache-dir uv
             uv sync --dev
             uv run ruff format --check .