fix: select deterministic ports for nginx

[vitormattos]

• Prefer 80/443 for nginx and fallback sequentially when ports are busy.
• Keep multiple checkouts isolated by Compose project.
• Preserve explicit HTTP_PORT, HTTPS_PORT and IP_BIND overrides.
• Display a final environment banner with the actual published URLs.
• Report optional services such as Mailpit and Playwright when available.

The developer workflow remains:

docker compose up

Example of docker service log:

nextcloud-1            | ✅ Database 🐬mysql ready
nextcloud-1            | 📅 Running cron for the first time ...
nextcloud-1            | Starting PHP-FPM...
nextcloud-1            | [18-Aug-2026 17:24:06] NOTICE: fpm is running, pid 1
nextcloud-1            | [18-Aug-2026 17:24:06] NOTICE: ready to handle connections
nextcloud-1            | 
nextcloud-1            | ┌─ 💙 Environment ready ─────────────────────
nextcloud-1            | │
nextcloud-1            | │ Nextcloud HTTP   http://localhost
nextcloud-1            | │ Nextcloud HTTPS  https://localhost
nextcloud-1            | │ Mailpit          http://localhost:8031
nextcloud-1            | │
nextcloud-1            | │ Nextcloud branch master
nextcloud-1            | │ Admin user       admin
nextcloud-1            | │ Admin password   admin
nextcloud-1            | │
nextcloud-1            | └────────────────────────────────────────────
nginx-port-selector-1  | ✅ Port selection complete. Exiting normally.
nginx-port-selector-1 exited with code 0