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/Http/Requests/Api/V1/StoreRegistrationFormFieldRequest.php

@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Requests\Api\V1;
+
+use App\Enums\RegistrationFieldType;
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+final class StoreRegistrationFormFieldRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /** @return array<string, mixed> */
+    public function rules(): array
+    {
+        $fieldType = $this->input('field_type');
+        $type = RegistrationFieldType::tryFrom($fieldType);
+
+        return [
+            'label' => ['required', 'string', 'max:255'],
+            'field_type' => ['required', Rule::in(array_column(RegistrationFieldType::cases(), 'value'))],
+            'options' => [
+                $type?->requiresOptions() ? 'required' : 'nullable',
+                $type?->prohibitsOptions() ? 'prohibited' : 'nullable',
+                'array',
+            ],
+            'options.*' => ['string', 'max:255'],
+            'tag_category' => [
+                $type === RegistrationFieldType::TAG_PICKER ? 'nullable' : 'prohibited',
+                'string',
+                'max:50',
+            ],
+            'is_required' => ['nullable', 'boolean'],
+            'is_portal_visible' => ['nullable', 'boolean'],
+            'is_admin_only' => ['nullable', 'boolean'],
+            'is_filterable' => ['nullable', 'boolean'],
+            'section' => ['nullable', 'string', 'max:100'],
+            'help_text' => ['nullable', 'string', 'max:5000'],
+            'sort_order' => ['nullable', 'integer', 'min:0'],
+        ];
+    }
+}