Refactor Docker Compose examples and plugins, add pytest tests

- Adjusted Compose files to build images locally instead of pulling.
- Simplified examples by removing `/etc/hosts` entry instructions.
- Enhanced `cloudflare.py` plugin with a configurable log format.
- Improved `generate-keys.sh` for portability using `$SCRIPT_DIR`.
- Added end-to-end tests for Compose examples using pytest.

examples/docker/python-app/Dockerfile

@@ -0,0 +1,11 @@
+FROM python:3.12-slim
+
+WORKDIR /app
+
+COPY server.py .
+
+RUN chmod +x server.py
+
+EXPOSE 8080
+
+CMD ["python3", "server.py"]