Restructure src/ and tests/ from package-by-type to package-by-domain

All classes are now organised by domain (Availability, Booking, Auth).
Each domain package contains its value object, repository, admin controller,
REST endpoint, and any shortcode pages under a matching sub-namespace.
Cross-cutting wiring (Plugin, AdminMenu, RestRegistrar, ShortcodeRegistrar,
Schema) lives at src/ root. Tests mirror the domain structure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/Booking/BookingRepository.php

@@ -0,0 +1,116 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Booking;
+
+class BookingRepository {
+
+	private string $table;
+
+	public function __construct( private \wpdb $db ) {
+		$this->table = $db->prefix . 'us_lessons';
+	}
+
+	public function insert( Lesson $lesson ): int {
+		$this->db->insert(
+			$this->table,
+			[
+				'slot_id'       => $lesson->slotId,
+				'student_id'    => $lesson->studentId,
+				'instructor_id' => $lesson->instructorId,
+				'status'        => $lesson->status,
+				'notes'         => $lesson->notes,
+				'created_at'    => current_time( 'mysql' ),
+			],
+			[ '%d', '%d', '%d', '%s', '%s', '%s' ]
+		);
+
+		return $this->db->insert_id;
+	}
+
+	public function findById( int $id ): ?Lesson {
+		$row = $this->db->get_row(
+			$this->db->prepare( "SELECT * FROM {$this->table} WHERE id = %d", $id )
+		);
+
+		return $row ? Lesson::fromRow( $row ) : null;
+	}
+
+	/**
+	 * Upcoming lessons for an instructor (status != cancelled, slot in the future).
+	 *
+	 * @return list<Lesson>
+	 */
+	public function findUpcomingForInstructor( int $instructorId ): array {
+		$avTable = str_replace( 'us_lessons', 'us_availability', $this->table );
+
+		$rows = $this->db->get_results(
+			$this->db->prepare(
+				"SELECT l.* FROM {$this->table} l
+                 JOIN {$avTable} a ON a.id = l.slot_id
+                 WHERE l.instructor_id = %d
+                   AND l.status != %s
+                   AND a.start_dt >= %s
+                 ORDER BY a.start_dt ASC",
+				$instructorId,
+				Lesson::STATUS_CANCELLED,
+				current_time( 'mysql' )
+			)
+		);
+
+		return array_map( Lesson::fromRow( ... ), $rows ?? [] );
+	}
+
+	/**
+	 * All lessons for a student.
+	 *
+	 * @return list<Lesson>
+	 */
+	public function findByStudent( int $studentId ): array {
+		$rows = $this->db->get_results(
+			$this->db->prepare(
+				"SELECT * FROM {$this->table} WHERE student_id = %d ORDER BY created_at DESC",
+				$studentId
+			)
+		);
+
+		return array_map( Lesson::fromRow( ... ), $rows ?? [] );
+	}
+
+	/**
+	 * All upcoming lessons across all instructors (admin view).
+	 *
+	 * @return list<Lesson>
+	 */
+	public function findAllUpcoming(): array {
+		$avTable = str_replace( 'us_lessons', 'us_availability', $this->table );
+
+		$rows = $this->db->get_results(
+			$this->db->prepare(
+				"SELECT l.* FROM {$this->table} l
+                 JOIN {$avTable} a ON a.id = l.slot_id
+                 WHERE l.status != %s
+                   AND a.start_dt >= %s
+                 ORDER BY a.start_dt ASC",
+				Lesson::STATUS_CANCELLED,
+				current_time( 'mysql' )
+			)
+		);
+
+		return array_map( Lesson::fromRow( ... ), $rows ?? [] );
+	}
+
+	public function updateStatus( int $id, string $status ): bool {
+		if ( ! in_array( $status, Lesson::VALID_STATUSES, true ) ) {
+			return false;
+		}
+
+		return (bool) $this->db->update(
+			$this->table,
+			[ 'status' => $status ],
+			[ 'id' => $id ],
+			[ '%s' ],
+			[ '%d' ]
+		);
+	}
+}