feat: refactor python-sandbox to standalone server

[thomwiggers]

Following the initial hardening in #212, this PR refactors the python-sandbox into a standalone HTTP server.

Major Changes:

• Sandbox Refactoring: python-sandbox/entrypoint.py is now a lightweight HTTP server. Each execution request spawns a new subprocess which is terminated after 5 seconds, ensuring a fresh environment and preventing persistent state or resource leaks.
• Removed Docker Dependency: The PythonPlugin now communicates via HTTP instead of executing docker run. This allows running the bot without access to the Docker socket.
• Docker Compose: Added docker-compose.yml to orchestrate both services, including network isolation (internal network for the sandbox).

Benefits:

• Improved Security: The bot no longer needs access to /var/run/docker.sock.
• Better Isolation: The sandbox server runs in its own network and uses its own resource limits.
• Simpler Deployment: Services can be easily managed with Docker Compose.

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