feat: registration form fields, section preferences, tag sync & schema updates

Implement EAV system for dynamic event-specific registration fields
with organisation-level templates, person section preferences with
priority ranking, and TagSyncService for deferred tag_picker sync.

New tables: registration_field_templates, registration_form_fields,
person_field_values, person_section_preferences.
New columns: persons.remarks, events.registration_show_section_preferences,
events.registration_show_availability.

58 tests, 126 assertions — all 432 tests pass (zero regressions).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Enums/RegistrationFieldType.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums;
+
+enum RegistrationFieldType: string
+{
+    case TEXT = 'text';
+    case TEXTAREA = 'textarea';
+    case SELECT = 'select';
+    case MULTISELECT = 'multiselect';
+    case CHECKBOX = 'checkbox';
+    case RADIO = 'radio';
+    case BOOLEAN = 'boolean';
+    case NUMBER = 'number';
+    case TAG_PICKER = 'tag_picker';
+
+    public function isMultiValue(): bool
+    {
+        return in_array($this, [self::MULTISELECT, self::CHECKBOX, self::TAG_PICKER], true);
+    }
+
+    public function requiresOptions(): bool
+    {
+        return in_array($this, [self::SELECT, self::MULTISELECT, self::RADIO, self::CHECKBOX], true);
+    }
+
+    public function prohibitsOptions(): bool
+    {
+        return in_array($this, [self::TEXT, self::TEXTAREA, self::BOOLEAN, self::NUMBER, self::TAG_PICKER], true);
+    }
+}