feat: #3624434Ship a front page describing the API and its documentation

Issue #3624434

A site installed with this template came up with a working API and nothing that says so. This adds a page that explains what the API serves and how to read it.

What this adds

• modules/contrib/webpage/recipes/default, first in the list because it installs Node, Display Builder and the editorial workflow. This template had no content type to build a page with.
• content/ with the page and its /api-and-docs alias.

The page is written for this template, not copied

The equivalent page in the Webships Starter links to /api/node/webapp and /api/node/organization. This template has no gallery content model, so those links would be dead here. This page points at /api, the resource list, and explains that every content type the site owner adds appears there.

Two things worth your eye

1. The page renders inside the administration theme. This template sets default_admin as the default theme, front end included.
2. The page describes the Swagger UI rather than linking to it: that route needs the access openapi api docs permission, which anonymous does not hold. Granting it would make a public documentation link possible, and is your call.

Checkpoints

• The page links only to routes this template actually serves
• CI is green
• Installed and checked on a real build
• Reviewed by the maintainer

AI-Generated: Yes