Accepted course applications now continue into the real course checkout

YogaBible's application wizard now sends accepted teacher-training applicants
to BookingBible's native course checkout. The Preparation Phase is a course
deposit—not a separate pass—so the payment, remaining balance, receipt,
reporting, enrollment, track, and access stages all stay on the same course
record.

The 4-, 8-, and 18-week programs use their existing live cohorts. The 18-week
application also carries the applicant's Weekday or Weekend track into checkout
and locks it to that accepted application. Applicants sign in with the same
email they used in the wizard before BookingBible can reserve a place or create
a Stripe payment.

Applicants choose whether they are buying as an individual or a company.
Individuals keep the course's configured VAT exemption. Companies provide the
company name, VAT/CVR number, participant names, and an optional shared note;
the three current YogaBible programs add the configured 25% VAT on top. These
details follow the enrollment and invoice without being placed in the payment
URL.

Application payment links expire after seven days and only work for the
accepted applicant, course, purchaser type, and track. Preparing or sharing a
link does not give access or reserve a place by itself; enrollment and access
begin through the normal course checkout.

Deployments must configure a stable, server-only
`COURSE_APPLICATION_HANDOFF_SECRET` of at least 32 characters. Staging and
production must use different values; rotating a value invalidates links that
have already been issued in that environment.

Course access stages are also easier to maintain on smaller screens. Fee and
allowance controls now stack cleanly, and each stage has a visible Remove stage
action with confirmation. A course must always retain at least one stage, and a
removal remains reversible until the editor is saved.