Docs: Write Deployment and Configuration Guide

[maximilien]

Summary

Document deployment and configuration behavior for the TODO demo in its sandbox-style runtime.

Audience

Developers and internal demo maintainers.

Scope

• environment variables
• runtime and port config
• Docker/runtime notes
• deployment assumptions and caveats

Source material

• Dockerfile
• entrypoint.sh
• blaxel.toml
• package.json

Definition of done

• config details are source-backed
• no unsupported infra claims
• practical enough for demo setup and operations
• written in Markdown

Assignee

Technical Writer 2