feat(llamabot/cli)📊: Add visualization command to CLI

[ericmjl]

• Introduce a new command 'visualize' in the CLI to launch a web app for visualizing prompts and messages.
• Create a new module 'visualize.py' under 'llamabot/cli' to handle the visualization logic.
• Implement a FastAPI application in 'llamabot/web/app.py' to serve the visualization interface.
• Add necessary static files and templates for the web interface.
• Update dependencies in 'pyproject.toml' and 'pixi.lock' to include FastAPI and Uvicorn.