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/ImportFromEventRequest.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Requests\Api\V1;
+
+use App\Models\Event;
+use Illuminate\Foundation\Http\FormRequest;
+
+final class ImportFromEventRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /** @return array<string, mixed> */
+    public function rules(): array
+    {
+        return [
+            'source_event_id' => ['required', 'ulid', 'exists:events,id'],
+        ];
+    }
+
+    public function withValidator($validator): void
+    {
+        $validator->after(function ($validator) {
+            $sourceEventId = $this->input('source_event_id');
+            if (!$sourceEventId) {
+                return;
+            }
+
+            $sourceEvent = Event::find($sourceEventId);
+            $targetEvent = $this->route('event');
+
+            if ($sourceEvent && $targetEvent && $sourceEvent->organisation_id !== $targetEvent->organisation_id) {
+                $validator->errors()->add('source_event_id', 'Source event must belong to the same organisation.');
+            }
+        });
+    }
+}