Add Registration Questions domain (per-offering intake forms)

Implements #5: studio admin / instructors author intake questions scoped
per offering; answers are stored against a lesson or group enrolment via a
polymorphic registration reference.

- src/Registration/: Question + Answer value objects, QuestionRepository
  and AnswerRepository, QuestionEndpoint (REST), QuestionController +
  templates/admin/questions.php (Offerings -> Questions submenu)
- us_questions and us_question_answers tables in Schema.php
- REST: public GET /offerings/{id}/questions; POST/PATCH/DELETE /questions
  gated by manage_questions + offering ownership (owner or studio admin)
- Field types text/textarea/select/checkbox; select options stored as JSON
- Wiring in Plugin, RestRegistrar, AdminMenu

AnswerRepository is built now and consumed by the booking/enrolment flow
in #3/#4.

Tests: tests/Unit/Registration/ (19 tests). composer test (63 total), cs,
and PHPStan level 6 all pass.

Refs #5

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

tests/Unit/Registration/QuestionRepositoryTest.php

@@ -0,0 +1,152 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Tests\Unit\Registration;
+
+use Brain\Monkey\Functions;
+use Mockery;
+use Unsupervised\Schedular\Registration\Question;
+use Unsupervised\Schedular\Registration\QuestionRepository;
+use Unsupervised\Schedular\Tests\Unit\TestCase;
+
+class QuestionRepositoryTest extends TestCase
+{
+    private \wpdb $db;
+    private QuestionRepository $repo;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->db         = Mockery::mock(\wpdb::class);
+        $this->db->prefix = 'wp_';
+        $this->repo       = new QuestionRepository($this->db);
+    }
+
+    public function testInsertWithNullOptionsStoresNull(): void
+    {
+        Functions\expect('current_time')->with('mysql')->andReturn('2026-04-01 12:00:00');
+
+        $this->db->shouldReceive('insert')
+            ->once()
+            ->with(
+                'wp_us_questions',
+                Mockery::on(static function (array $data): bool {
+                    return $data['offering_id'] === 7
+                        && $data['label'] === 'Your level?'
+                        && $data['field_type'] === Question::FIELD_TEXT
+                        && $data['options'] === null
+                        && $data['is_required'] === 0
+                        && $data['created_at'] === '2026-04-01 12:00:00';
+                }),
+                Mockery::type('array')
+            );
+
+        $this->db->insert_id = 21;
+
+        $question = new Question(7, 'Your level?');
+
+        self::assertSame(21, $this->repo->insert($question));
+    }
+
+    public function testInsertEncodesOptionsAsJson(): void
+    {
+        Functions\expect('current_time')->andReturn('2026-04-01 12:00:00');
+        Functions\expect('wp_json_encode')
+            ->once()
+            ->with(['Beginner', 'Advanced'])
+            ->andReturn('["Beginner","Advanced"]');
+
+        $this->db->shouldReceive('insert')
+            ->once()
+            ->with(
+                'wp_us_questions',
+                Mockery::on(static fn (array $data): bool => $data['options'] === '["Beginner","Advanced"]'),
+                Mockery::type('array')
+            );
+
+        $this->db->insert_id = 22;
+
+        $question = new Question(
+            offeringId: 7,
+            label:      'Pick a level',
+            fieldType:  Question::FIELD_SELECT,
+            options:    ['Beginner', 'Advanced'],
+        );
+
+        self::assertSame(22, $this->repo->insert($question));
+    }
+
+    public function testUpdateReturnsTrueOnSuccess(): void
+    {
+        $this->db->shouldReceive('update')
+            ->once()
+            ->with(
+                'wp_us_questions',
+                Mockery::on(static fn (array $data): bool => $data['label'] === 'Renamed' && $data['is_required'] === 1),
+                ['id' => 5],
+                Mockery::type('array'),
+                ['%d']
+            )
+            ->andReturn(1);
+
+        $question = new Question(7, 'Renamed', isRequired: true, id: 5);
+
+        self::assertTrue($this->repo->update(5, $question));
+    }
+
+    public function testFindByOfferingActiveOnlyPreparesQuery(): void
+    {
+        $this->db->shouldReceive('prepare')
+            ->once()
+            ->with(
+                Mockery::pattern('/offering_id = %d AND is_active = %d/'),
+                Mockery::on(static fn (array $p): bool => $p === [7, 1])
+            )
+            ->andReturn('SELECT ...');
+
+        $this->db->shouldReceive('get_results')->andReturn([]);
+
+        self::assertSame([], $this->repo->findByOffering(7, activeOnly: true));
+    }
+
+    public function testFindByOfferingReturnsQuestions(): void
+    {
+        $row = (object) [
+            'id'          => '3',
+            'offering_id' => '7',
+            'label'       => 'Q',
+            'field_type'  => Question::FIELD_TEXT,
+            'options'     => null,
+            'is_required' => '0',
+            'sort_order'  => '0',
+            'is_active'   => '1',
+        ];
+
+        $this->db->shouldReceive('prepare')->andReturn('SELECT ...');
+        $this->db->shouldReceive('get_results')->andReturn([$row]);
+
+        $questions = $this->repo->findByOffering(7);
+
+        self::assertCount(1, $questions);
+        self::assertInstanceOf(Question::class, $questions[0]);
+    }
+
+    public function testFindByIdReturnsNullWhenNotFound(): void
+    {
+        $this->db->shouldReceive('prepare')->andReturn('SELECT ...');
+        $this->db->shouldReceive('get_row')->andReturn(null);
+
+        self::assertNull($this->repo->findById(99));
+    }
+
+    public function testDeleteCallsWpdbDelete(): void
+    {
+        $this->db->shouldReceive('delete')
+            ->once()
+            ->with('wp_us_questions', ['id' => 4], ['%d'])
+            ->andReturn(1);
+
+        self::assertTrue($this->repo->delete(4));
+    }
+}