feat: person identity matching with detection, confirmation and audit trail

Implements enterprise-grade identity resolution (detect → suggest → confirm)
for Person ↔ User linking. Matches are detected automatically on person
creation and user account creation, then surfaced to organisers for explicit
confirmation or dismissal. No silent auto-linking.

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

api/app/Enums/IdentityMatchStatus.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums;
+
+enum IdentityMatchStatus: string
+{
+    case PENDING = 'pending';
+    case CONFIRMED = 'confirmed';
+    case DISMISSED = 'dismissed';
+}