Automatic app embed detection in the theme editor

Turning on the storefront widget in your theme editor is easier to get right. When you open the theme editor from the setup step, Easy Appointment Booking now detects the app embed automatically and confirms it's on, so you no longer need to click a separate "I've enabled it" button. The step also shows a diagram with numbered callouts pointing at the app switch and the Save button, so it's clear what to click before you save.