docs(readme): refresh outdated requirements, distros, links, and command list

[mrrobot47]

Summary

The README had drifted from the codebase on every factual claim checked. This refreshes the stale content. All changes verified against composer.json, the CI workflow, and the linked repos.

Changes

Was	Now	Why
PHP CLI >=7.1	>=7.4	7.1 matched nothing — composer.json requires >=7.0, platform is 7.3, CI tests 7.4–8.5. PHP 7.0–7.3 are EOL/untested.
Ubuntu 14.04/16.04/18.04/20.04/22.04, Debian 8/10	Ubuntu 20.04/22.04/24.04, Debian 11/12	14.04/16.04/18.04 and Debian 8/10 are all EOL; current LTS releases were missing.
Tab-completion link → develop-v4	→ master	develop-v4 is frozen at 2018-11-22 (thousands of commits behind).
site-wp-command link	site-type-wp	Repo was renamed; the old URL only redirects.
Bundled commands = site + shell	All 10 bundled top-level commands + site types	composer.json bundles admin-tools, auth, config, cron, dash, log, mailhog, service, shell, site (+ site-type-php/wp).

Notes

• Tested-distro list is a best-effort update to current LTS releases — please confirm against the installer's actual test matrix (Debian 13/trixie could be added if validated for the host installer).
• The PHP Modules line (curl, sqlite3, pcntl) was left unchanged.