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>

tests/Unit/Auth/RoleManagerTest.php

@@ -1,10 +1,10 @@
 <?php
 declare(strict_types=1);
 
-namespace Unsupervised\Schedular\Tests\Unit\Roles;
+namespace Unsupervised\Schedular\Tests\Unit\Auth;
 
 use Brain\Monkey\Functions;
-use Unsupervised\Schedular\Roles\RoleManager;
+use Unsupervised\Schedular\Auth\RoleManager;
 use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class RoleManagerTest extends TestCase

tests/Unit/Availability/AvailabilityRepositoryTest.php

@@ -1,12 +1,12 @@
 <?php
 declare(strict_types=1);
 
-namespace Unsupervised\Schedular\Tests\Unit\Data;
+namespace Unsupervised\Schedular\Tests\Unit\Availability;
 
 use Brain\Monkey\Functions;
 use Mockery;
-use Unsupervised\Schedular\Data\AvailabilityRepository;
-use Unsupervised\Schedular\Model\AvailabilitySlot;
+use Unsupervised\Schedular\Availability\AvailabilityRepository;
+use Unsupervised\Schedular\Availability\AvailabilitySlot;
 use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class AvailabilityRepositoryTest extends TestCase
@@ -18,9 +18,9 @@ class AvailabilityRepositoryTest extends TestCase
     {
         parent::setUp();
 
-        $this->db       = Mockery::mock(\wpdb::class);
+        $this->db         = Mockery::mock(\wpdb::class);
         $this->db->prefix = 'wp_';
-        $this->repo     = new AvailabilityRepository($this->db);
+        $this->repo       = new AvailabilityRepository($this->db);
     }
 
     public function testInsertCallsWpdbInsertAndReturnsId(): void

tests/Unit/Availability/AvailabilitySlotTest.php

@@ -1,9 +1,9 @@
 <?php
 declare(strict_types=1);
 
-namespace Unsupervised\Schedular\Tests\Unit\Model;
+namespace Unsupervised\Schedular\Tests\Unit\Availability;
 
-use Unsupervised\Schedular\Model\AvailabilitySlot;
+use Unsupervised\Schedular\Availability\AvailabilitySlot;
 use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class AvailabilitySlotTest extends TestCase

tests/Unit/Booking/BookingRepositoryTest.php

@@ -1,12 +1,12 @@
 <?php
 declare(strict_types=1);
 
-namespace Unsupervised\Schedular\Tests\Unit\Data;
+namespace Unsupervised\Schedular\Tests\Unit\Booking;
 
 use Brain\Monkey\Functions;
 use Mockery;
-use Unsupervised\Schedular\Data\BookingRepository;
-use Unsupervised\Schedular\Model\Lesson;
+use Unsupervised\Schedular\Booking\BookingRepository;
+use Unsupervised\Schedular\Booking\Lesson;
 use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class BookingRepositoryTest extends TestCase

tests/Unit/Booking/LessonTest.php

@@ -1,9 +1,9 @@
 <?php
 declare(strict_types=1);
 
-namespace Unsupervised\Schedular\Tests\Unit\Model;
+namespace Unsupervised\Schedular\Tests\Unit\Booking;
 
-use Unsupervised\Schedular\Model\Lesson;
+use Unsupervised\Schedular\Booking\Lesson;
 use Unsupervised\Schedular\Tests\Unit\TestCase;
 
 class LessonTest extends TestCase