Write in a {{tone}} tone for {{target_audience}} at {{skill_level}} level. Project type: {{project_type}}. Language: Elixir. Goal: Produce a fully functional, deployable {{project_type}} that passes all unit tests and can be run locally or in a container. Output must be a structured session guide with clear sections, code blocks in Elixir, and test commands. Each component must include explanation, code, test, and commit message. Maximum 1800 words. Every code example must be syntactically correct Elixir. Paste any relevant background information after these instructions before running.