Issue #3611530: Add a no-code Getting started guide and expand the calendar/site-builder documentation

Adds a task-oriented, no-code Getting started walkthrough (enable modules, create a resource, publish slots, place the calendar, take and confirm a booking) and a How to use it section to the Calendar page - the docs so far were developer/architecture oriented with no hands-on guide. Also refreshes stale documentation: the README/architecture module tables and several pages still used the old booking_* module names and pre-rename Booking title; updated to the real yoyaku_* names and current module statuses, and linked the published docs site from the README. Documentation only; no code changes.