Add Quick Run section with complete getting-started workflow including
admin user creation via --execute flag. Consolidate Docker Compose to
treat reverse proxy as essential with Traefik/Caddy/nginx examples.
Move detailed image building to development guide, keeping deployment
docs focused on using pre-built images.
Create environment variables reference with practical examples and
context. Clarify built-in TLS is for testing only; production should
use reverse proxies.
- Change xtasks to use `clap` for argument parsing
- Generate admin command reference manually instead of with `clap_markdown`
- Split admin command reference into multiple files
