Expand documentation: Docker usage, module development, and audit existing docs

[andrewmarconi]

Summary

Improve project documentation to cover key gaps for end users, administrators, and module developers. Also audit existing documentation to ensure it remains accurate and up to date.

Tasks

1. Docker deployment guide (end users / admins)

• Document how to pull and run the Docker image
• Cover environment variables and configuration options
• Include common operational tasks (starting, stopping, updating, viewing logs)
• Add troubleshooting tips for common Docker issues

2. Module development guide (developers)

• Explain the module architecture and lifecycle
• Provide a step-by-step walkthrough for creating a new module
• Document the module API surface (types, hooks, theme tokens, actions)
• Include a minimal example module as a reference

3. Audit existing documentation

• Review all files in docs/ for accuracy against current codebase
• Update any outdated instructions, references, or screenshots
• Remove or flag any documentation for features that no longer exist

Acceptance Criteria

• Users can deploy and operate the app via Docker using only the documentation
• Developers can create a new module end-to-end following the guide
• All existing docs reflect the current state of the project