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/Models/Person.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Models;
 
+use App\Enums\IdentityMatchStatus;
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Concerns\HasUlids;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
@@ -11,6 +12,7 @@ use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasOne;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
 final class Person extends Model
@@ -74,6 +76,17 @@ final class Person extends Model
         return $this->hasMany(ShiftAssignment::class);
     }
 
+    public function identityMatches(): HasMany
+    {
+        return $this->hasMany(PersonIdentityMatch::class);
+    }
+
+    public function pendingIdentityMatch(): HasOne
+    {
+        return $this->hasOne(PersonIdentityMatch::class)
+            ->where('status', IdentityMatchStatus::PENDING);
+    }
+
     public function scopeApproved(Builder $query): Builder
     {
         return $query->where('status', 'approved');