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/database/migrations/2026_04_10_200000_create_person_identity_matches_table.php

@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('person_identity_matches', function (Blueprint $table) {
+            $table->ulid('id')->primary();
+
+            $table->foreignUlid('person_id')
+                ->constrained('persons')
+                ->cascadeOnDelete();
+
+            $table->foreignUlid('matched_user_id')
+                ->constrained('users')
+                ->cascadeOnDelete();
+
+            $table->string('matched_on');
+            $table->string('confidence');
+            $table->string('status')->default('pending');
+
+            $table->foreignUlid('resolved_by_user_id')
+                ->nullable()
+                ->constrained('users')
+                ->nullOnDelete();
+
+            $table->timestamp('resolved_at')->nullable();
+            $table->timestamp('created_at')->nullable();
+
+            // Prevent duplicate match records for the same person+user pair
+            $table->unique(['person_id', 'matched_user_id']);
+
+            // Query indexes
+            $table->index(['person_id', 'status']);
+            $table->index(['matched_user_id', 'status']);
+            $table->index('status');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('person_identity_matches');
+    }
+};