Add mypy to the CI

.woodpecker/check.yaml

@@ -10,5 +10,7 @@ steps:
       - uv sync --all-extras
       # Lint the code
       - uv run ruff check src/xmpp_api/
+      # Check for type safety
+      - uv run mypy src/xmpp_api/
       # Check for security issues
       - uv run bandit -r src/xmpp_api/