Let the studio book lessons and record intake collected elsewhere

Two related gaps, closed together because the second is created by the first.

A private lesson could only be booked by the student or their guardian, so a
booking taken over the phone had no way in — where group classes have had "Add
students directly" all along. "Book a lesson for a student" is now a panel on
Scheduler and My Lessons: student, open time, lesson type, with weekly term
reservations and a no-charge option for make-up lessons. The booking core is
extracted to Booking\LessonBooker and shared with POST /bookings, so the two
paths cannot drift on offering rules, slot claiming, or billing.

That leaves a registration with no intake answers and no policy acceptances,
because nobody was at a keyboard to give them — already true of every directly
added group-class student. Ticking the boxes on a student's behalf would be an
audit trail that says something untrue, so instead the answers are collected
another way and recorded afterwards, from a lesson's or an enrolment's detail
page. Every recording must say how it was collected, which is stamped on each
row along with who typed it and shown in a new "How it was given" column: a
policy ticked online and one transcribed from paper must never look alike.

Only staff-made registrations qualify (us_lessons.booked_by,
us_group_enrollments.enrolled_by) — one the student made already holds their
own answers. Only what is still missing can be recorded, re-checked at write
time, so a stale or double-posted form cannot duplicate or overwrite. No IP is
stored for a transcription, and accepted_by stays the student while recorded_by
names the staff member.

Intake is now generic over Registration\IntakeSubject, which Lesson and
Enrollment both implement; LessonDetail became Registration\IntakeAudit and is
shared by both detail views rather than duplicated.

Closes #182

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01QfHt6CyJHz6KkA4RuaS7WK

CHANGELOG.md

@@ -13,6 +13,10 @@ each change under the current top section as you work.
 
 ## [1.5.3]
 
+### Added
+- **Intake answers and policy agreements can now be recorded after the fact for a lesson the studio booked, or a student it added straight into a group class.** A lesson booked from wp-admin has no answers and no signed policies — nobody was at a keyboard to give them — and until now there was nowhere to put them once the studio did collect them at the first lesson or over the phone. The lesson's detail page now carries **Record intake collected elsewhere**, offering whatever is still outstanding: the unanswered questions and the policy versions with no acceptance on file. Fill in what you have, leave the rest, come back later — nothing already recorded can be overwritten, and a form posted twice cannot duplicate anything. Every recording must say **how** it was collected — a signed paper form, in person, over the phone, by email, or some other way you describe — and that answer is stamped on each entry along with your name. Both audit tables gained a **How it was given** column, so a policy accepted online and one transcribed from paper can never again look like the same thing. Only registrations the studio made have the panel: one a student made already holds their own answers, and those stay theirs alone. Group classes work the same way, reached from the new **Intake → View** link on each roster row of a class's detail page — a student added with **Add students directly** was never shown the enrolment form, and this is where what you collect instead now goes.
+- **You can now book a lesson for a student yourself, from Scheduler or My Lessons.** Group classes have always had **Add students directly**, but a private lesson could only be booked by the student — or by their parent, for a child — so a booking taken over the phone, or a make-up lesson an instructor wanted to slot in, had no way in short of asking the family to go and do it themselves. **Book a lesson for a student**, a panel at the top of both lesson pages, takes the student, an open time and the lesson type and books it there and then. Tick **Reserve this time weekly** to hold the same time for the rest of the term, or **No charge** for a make-up or goodwill lesson — that one skips payment entirely and confirms the lesson immediately, where an ordinary booking raises a pending payment at the lesson type's price and confirms when it settles, exactly as a student's own booking does. The **Scheduler** reaches every instructor's open times; **My Lessons** shows an instructor only their own. Booking this way does not ask the intake questions or record the policy agreements the student would give themselves — those stay theirs to answer, so a lesson booked for someone simply shows none on its detail page.
+
 ## [1.5.2]
 
 ### Added