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/Resources/Api/V1/PersonResource.php

@@ -23,6 +23,7 @@ final class PersonResource extends JsonResource
             'status' => $this->status,
             'is_blacklisted' => $this->is_blacklisted,
             'admin_notes' => $this->admin_notes,
+            'remarks' => $this->remarks,
             'custom_fields' => $this->custom_fields,
             'created_at' => $this->created_at->toIso8601String(),
             'crowd_type' => new CrowdTypeResource($this->whenLoaded('crowdType')),
@@ -53,6 +54,8 @@ final class PersonResource extends JsonResource
                     'added_by_user_id' => $this->pivot->added_by_user_id,
                 ]
             ),
+            'field_values' => PersonFieldValueResource::collection($this->whenLoaded('fieldValues')),
+            'section_preferences' => PersonSectionPreferenceResource::collection($this->whenLoaded('sectionPreferences')),
             'tags' => $this->when(
                 $this->user_id && $this->relationLoaded('user'),
                 function () {