Add e-transfer destination email (studio default + offering/booking overrides)

The e-transfer destination is resolved at booking time (offering override ->
studio default) and frozen onto the payment, so each record keeps where the
student was directed. It can then be corrected per booking.

- StudioSettings: us_etransfer_email option + a Default e-transfer email field
  on the Studio Settings page.
- Offering: etransfer_email column/field (instructor override) across VO, repo,
  REST endpoint, admin controller, and form.
- Payment: etransfer_email column on the payment (frozen record) +
  PaymentRepository::updateEtransferEmail; PaymentService freezes it from the
  offering override or studio default at creation; booking/enrolment pass the
  offering override.
- My Lessons: instructors edit the e-transfer email per pending lesson payment
  (ownership-checked).
- Payments queue: studio admin can correct the email at confirmation (for when
  a student sends it to the wrong place).
- Docs updated.

Tests: Payment/Offering rows + PaymentService freezing. composer test (148),
cs, and PHPStan level 6 all pass.

Refs #7

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/Payment/PaymentService.php

@@ -19,15 +19,17 @@ class PaymentService {
 		private ReceiptMailer $mailer,
 		private BookingRepository $bookings,
 		private EnrollmentRepository $enrollments,
+		private StudioSettings $settings,
 	) {}
 
 	/**
 	 * Create the payment for a new registration and link it. Comped students are
 	 * marked paid and confirmed immediately; everyone else gets a pending payment
-	 * (card via Stripe — coming soon; e-transfer confirmed manually). Returns null
-	 * when the registration has no price to charge.
+	 * (card via Stripe — coming soon; e-transfer confirmed manually). The
+	 * e-transfer destination is frozen now from the offering override or the studio
+	 * default. Returns null when the registration has no price to charge.
 	 */
-	public function createForRegistration( string $type, int $registrationId, int $studentId, int $instructorId, float $amount, string $currency ): ?Payment {
+	public function createForRegistration( string $type, int $registrationId, int $studentId, int $instructorId, float $amount, string $currency, ?string $offeringEtransferEmail = null ): ?Payment {
 		if ( $amount <= 0.0 ) {
 			return null;
 		}
@@ -35,6 +37,10 @@ class PaymentService {
 		$method = $this->resolver->resolve( $studentId );
 		$status = Payment::METHOD_COMP === $method ? Payment::STATUS_PAID : Payment::STATUS_PENDING;
 
+		$etransferEmail = null !== $offeringEtransferEmail && '' !== $offeringEtransferEmail
+			? $offeringEtransferEmail
+			: ( '' !== $this->settings->etransferEmail() ? $this->settings->etransferEmail() : null );
+
 		$id = $this->payments->insert(
 			new Payment(
 				studentId:        $studentId,
@@ -45,6 +51,7 @@ class PaymentService {
 				currency:         $currency,
 				method:           $method,
 				status:           $status,
+				etransferEmail:   $etransferEmail,
 			)
 		);