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/Models/Event.php

@@ -66,6 +66,8 @@ final class Event extends Model
         'registration_banner_url',
         'registration_welcome_text',
         'registration_logo_url',
+        'registration_show_section_preferences',
+        'registration_show_availability',
     ];
 
     protected function casts(): array
@@ -76,6 +78,8 @@ final class Event extends Model
             'is_recurring' => 'boolean',
             'recurrence_exceptions' => 'array',
             'event_type' => 'string',
+            'registration_show_section_preferences' => 'boolean',
+            'registration_show_availability' => 'boolean',
         ];
     }