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/Offering/Offering.php

@@ -0,0 +1,90 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Offering;
+
+class Offering {
+
+	public const KIND_PRIVATE_LESSON = 'private_lesson';
+	public const KIND_GROUP_CLASS    = 'group_class';
+
+	/**
+	 * All valid offering kinds.
+	 *
+	 * @var list<string>
+	 */
+	public const VALID_KINDS = [ self::KIND_PRIVATE_LESSON, self::KIND_GROUP_CLASS ];
+
+	public const BILLING_ONE_TIME  = 'one_time';
+	public const BILLING_FULL_TERM = 'full_term';
+
+	/**
+	 * All valid billing modes.
+	 *
+	 * @var list<string>
+	 */
+	public const VALID_BILLING_MODES = [ self::BILLING_ONE_TIME, self::BILLING_FULL_TERM ];
+
+	public function __construct(
+		public readonly int $instructorId,
+		public readonly string $kind,
+		public readonly string $title,
+		public readonly int $priceCents = 0,
+		public readonly string $currency = 'CAD',
+		public readonly string $billingMode = self::BILLING_ONE_TIME,
+		public readonly ?string $description = null,
+		public readonly ?int $durationMinutes = null,
+		public readonly bool $allowWeekly = false,
+		public readonly ?int $capacity = null,
+		public readonly ?string $termStart = null,
+		public readonly ?string $termEnd = null,
+		public readonly ?string $scheduleNote = null,
+		public readonly bool $isActive = true,
+		public readonly ?int $id = null,
+	) {}
+
+	public static function fromRow( object $row ): self {
+		return new self(
+			instructorId:    (int) $row->instructor_id,
+			kind:            $row->kind,
+			title:           $row->title,
+			priceCents:      (int) $row->price_cents,
+			currency:        $row->currency,
+			billingMode:     $row->billing_mode,
+			description:     $row->description,
+			durationMinutes: null !== $row->duration_minutes ? (int) $row->duration_minutes : null,
+			allowWeekly:     (bool) $row->allow_weekly,
+			capacity:        null !== $row->capacity ? (int) $row->capacity : null,
+			termStart:       $row->term_start,
+			termEnd:         $row->term_end,
+			scheduleNote:    $row->schedule_note,
+			isActive:        (bool) $row->is_active,
+			id:              (int) $row->id,
+		);
+	}
+
+	/**
+	 * Returns a plain array representation of the offering.
+	 *
+	 * @return array<string, mixed>
+	 */
+	public function toArray(): array {
+		return [
+			'id'               => $this->id,
+			'instructor_id'    => $this->instructorId,
+			'kind'             => $this->kind,
+			'title'            => $this->title,
+			'description'      => $this->description,
+			'duration_minutes' => $this->durationMinutes,
+			'price_cents'      => $this->priceCents,
+			'currency'         => $this->currency,
+			'billing_mode'     => $this->billingMode,
+			'allow_weekly'     => $this->allowWeekly,
+			'capacity'         => $this->capacity,
+			'term_start'       => $this->termStart,
+			'term_end'         => $this->termEnd,
+			'schedule_note'    => $this->scheduleNote,
+			'is_active'        => $this->isActive,
+		];
+	}
+}