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/OfferingRepository.php

@@ -0,0 +1,107 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Offering;
+
+class OfferingRepository {
+
+	private string $table;
+
+	public function __construct( private \wpdb $db ) {
+		$this->table = $db->prefix . 'us_offerings';
+	}
+
+	public function insert( Offering $offering ): int {
+		$this->db->insert(
+			$this->table,
+			$this->columns( $offering ) + [ 'created_at' => current_time( 'mysql' ) ],
+			[ '%d', '%s', '%s', '%s', '%d', '%s', '%s', '%d', '%d', '%s', '%s', '%s', '%d', '%s' ]
+		);
+
+		return $this->db->insert_id;
+	}
+
+	public function update( int $id, Offering $offering ): bool {
+		return false !== $this->db->update(
+			$this->table,
+			$this->columns( $offering ),
+			[ 'id' => $id ],
+			[ '%d', '%s', '%s', '%s', '%d', '%s', '%s', '%d', '%d', '%s', '%s', '%s', '%d' ],
+			[ '%d' ]
+		);
+	}
+
+	/**
+	 * Column values shared by insert and update (excludes created_at).
+	 *
+	 * @return array<string, mixed>
+	 */
+	private function columns( Offering $offering ): array {
+		return [
+			'instructor_id'    => $offering->instructorId,
+			'kind'             => $offering->kind,
+			'title'            => $offering->title,
+			'description'      => $offering->description,
+			'duration_minutes' => $offering->durationMinutes,
+			'price_cents'      => $offering->priceCents,
+			'currency'         => $offering->currency,
+			'billing_mode'     => $offering->billingMode,
+			'allow_weekly'     => $offering->allowWeekly ? 1 : 0,
+			'capacity'         => $offering->capacity,
+			'term_start'       => $offering->termStart,
+			'term_end'         => $offering->termEnd,
+			'schedule_note'    => $offering->scheduleNote,
+			'is_active'        => $offering->isActive ? 1 : 0,
+		];
+	}
+
+	/**
+	 * Find offerings, optionally filtered by instructor, kind, and active state.
+	 *
+	 * @return list<Offering>
+	 */
+	public function findAll( int $instructorId = 0, string $kind = '', ?bool $activeOnly = null ): array {
+		$where  = [ '1 = 1' ];
+		$params = [];
+
+		if ( $instructorId > 0 ) {
+			$where[]  = 'instructor_id = %d';
+			$params[] = $instructorId;
+		}
+
+		if ( '' !== $kind ) {
+			$where[]  = 'kind = %s';
+			$params[] = $kind;
+		}
+
+		if ( null !== $activeOnly ) {
+			$where[]  = 'is_active = %d';
+			$params[] = $activeOnly ? 1 : 0;
+		}
+
+		$whereClause = implode( ' AND ', $where );
+		$sql         = "SELECT * FROM {$this->table} WHERE {$whereClause} ORDER BY title ASC";
+
+		$rows = $params
+			? $this->db->get_results( $this->db->prepare( $sql, $params ) )
+			: $this->db->get_results( $sql );
+
+		return array_map( Offering::fromRow( ... ), $rows ?? [] );
+	}
+
+	public function findById( int $id ): ?Offering {
+		$row = $this->db->get_row(
+			$this->db->prepare( "SELECT * FROM {$this->table} WHERE id = %d", $id )
+		);
+
+		return $row ? Offering::fromRow( $row ) : null;
+	}
+
+	public function delete( int $id ): bool {
+		return (bool) $this->db->delete(
+			$this->table,
+			[ 'id' => $id ],
+			[ '%d' ]
+		);
+	}
+}