Add Offerings domain and studio-admin capabilities

Implements the offerings catalog (#1): private-lesson types and group
classes carrying pricing, billing mode (one_time/full_term), duration,
capacity, and term details. Adds the src/Offering/ domain (value object,
repository, REST endpoint, admin controller + template), the us_offerings
table, and an Offerings admin page.

Also lands the capability slice of #9: registers the us_studio_admin role
and the new capability strings (manage_instructors, manage_offerings,
manage_questions, manage_policies, manage_billing, view_all_payments,
view_own_payments, export_payments) so offering management gates correctly.

Tests: tests/Unit/Offering/ (value object + repository) and a studio-admin
case in RoleManagerTest. composer test, cs, and PHPStan level 6 all pass.

Refs #1 #9

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RestRegistrar.php

@@ -7,6 +7,8 @@ use Unsupervised\Schedular\Availability\AvailabilityEndpoint;
 use Unsupervised\Schedular\Availability\AvailabilityRepository;
 use Unsupervised\Schedular\Booking\BookingEndpoint;
 use Unsupervised\Schedular\Booking\BookingRepository;
+use Unsupervised\Schedular\Offering\OfferingEndpoint;
+use Unsupervised\Schedular\Offering\OfferingRepository;
 
 class RestRegistrar {
 
@@ -14,10 +16,12 @@ class RestRegistrar {
 
 	private AvailabilityEndpoint $availabilityEndpoint;
 	private BookingEndpoint $bookingEndpoint;
+	private OfferingEndpoint $offeringEndpoint;
 
-	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings ) {
+	public function __construct( AvailabilityRepository $availability, BookingRepository $bookings, OfferingRepository $offerings ) {
 		$this->availabilityEndpoint = new AvailabilityEndpoint( $availability );
 		$this->bookingEndpoint      = new BookingEndpoint( $availability, $bookings );
+		$this->offeringEndpoint     = new OfferingEndpoint( $offerings );
 	}
 
 	public function register(): void {
@@ -27,5 +31,6 @@ class RestRegistrar {
 	public function registerRoutes(): void {
 		$this->availabilityEndpoint->registerRoutes( self::NAMESPACE );
 		$this->bookingEndpoint->registerRoutes( self::NAMESPACE );
+		$this->offeringEndpoint->registerRoutes( self::NAMESPACE );
 	}
 }