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/QuestionTest.php

@@ -0,0 +1,83 @@
+<?php
+declare(strict_types=1);
+
+namespace Unsupervised\Schedular\Tests\Unit\Registration;
+
+use Unsupervised\Schedular\Registration\Question;
+use Unsupervised\Schedular\Tests\Unit\TestCase;
+
+class QuestionTest extends TestCase
+{
+    public function testConstructorAndDefaults(): void
+    {
+        $question = new Question(7, 'Your level?');
+
+        self::assertSame(7, $question->offeringId);
+        self::assertSame('Your level?', $question->label);
+        self::assertSame(Question::FIELD_TEXT, $question->fieldType);
+        self::assertNull($question->options);
+        self::assertFalse($question->isRequired);
+        self::assertSame(0, $question->sortOrder);
+        self::assertTrue($question->isActive);
+        self::assertNull($question->id);
+    }
+
+    public function testFromRowDecodesOptionsJson(): void
+    {
+        $row = (object) [
+            'id'          => '3',
+            'offering_id' => '7',
+            'label'       => 'Pick a level',
+            'field_type'  => Question::FIELD_SELECT,
+            'options'     => '["Beginner","Advanced"]',
+            'is_required' => '1',
+            'sort_order'  => '2',
+            'is_active'   => '1',
+        ];
+
+        $question = Question::fromRow($row);
+
+        self::assertSame(3, $question->id);
+        self::assertSame(Question::FIELD_SELECT, $question->fieldType);
+        self::assertSame(['Beginner', 'Advanced'], $question->options);
+        self::assertTrue($question->isRequired);
+        self::assertSame(2, $question->sortOrder);
+    }
+
+    public function testFromRowHandlesNullOptions(): void
+    {
+        $row = (object) [
+            'id'          => '4',
+            'offering_id' => '7',
+            'label'       => 'Notes',
+            'field_type'  => Question::FIELD_TEXTAREA,
+            'options'     => null,
+            'is_required' => '0',
+            'sort_order'  => '0',
+            'is_active'   => '0',
+        ];
+
+        $question = Question::fromRow($row);
+
+        self::assertNull($question->options);
+        self::assertFalse($question->isActive);
+    }
+
+    public function testToArrayContainsExpectedKeys(): void
+    {
+        $question = new Question(7, 'Label', Question::FIELD_TEXT, id: 9);
+        $arr      = $question->toArray();
+
+        foreach (['id', 'offering_id', 'label', 'field_type', 'options', 'is_required', 'sort_order', 'is_active'] as $key) {
+            self::assertArrayHasKey($key, $arr);
+        }
+    }
+
+    public function testValidFieldTypeConstants(): void
+    {
+        self::assertContains(Question::FIELD_TEXT, Question::VALID_FIELD_TYPES);
+        self::assertContains(Question::FIELD_TEXTAREA, Question::VALID_FIELD_TYPES);
+        self::assertContains(Question::FIELD_SELECT, Question::VALID_FIELD_TYPES);
+        self::assertContains(Question::FIELD_CHECKBOX, Question::VALID_FIELD_TYPES);
+    }
+}