Add audit trail: AuditLog entity, AuditService, admin logs page

- AuditLog entity: action, entityType, entityId, data (JSON), performedBy, ipAddress
- AuditService: logs actions with current user and IP
- Audit on: order_created, order_paid, order_cancelled, order_refunded
- Admin /admin/logs: paginated table with action badges, details, user, IP
- Navigation link 'Logs' in admin header

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

tests/Entity/AuditLogTest.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Tests\Entity;
+
+use App\Entity\AuditLog;
+use PHPUnit\Framework\TestCase;
+
+class AuditLogTest extends TestCase
+{
+    public function testConstructor(): void
+    {
+        $log = new AuditLog('order_created', 'BilletBuyer', 42);
+
+        self::assertNull($log->getId());
+        self::assertSame('order_created', $log->getAction());
+        self::assertSame('BilletBuyer', $log->getEntityType());
+        self::assertSame(42, $log->getEntityId());
+        self::assertSame([], $log->getData());
+        self::assertNull($log->getPerformedBy());
+        self::assertNull($log->getIpAddress());
+        self::assertInstanceOf(\DateTimeImmutable::class, $log->getCreatedAt());
+    }
+
+    public function testSetData(): void
+    {
+        $log = new AuditLog('test', 'Entity');
+        $result = $log->setData(['key' => 'value']);
+
+        self::assertSame(['key' => 'value'], $log->getData());
+        self::assertSame($log, $result);
+    }
+
+    public function testSetPerformedBy(): void
+    {
+        $log = new AuditLog('test', 'Entity');
+        $result = $log->setPerformedBy('admin@test.fr');
+
+        self::assertSame('admin@test.fr', $log->getPerformedBy());
+        self::assertSame($log, $result);
+    }
+
+    public function testSetIpAddress(): void
+    {
+        $log = new AuditLog('test', 'Entity');
+        $result = $log->setIpAddress('127.0.0.1');
+
+        self::assertSame('127.0.0.1', $log->getIpAddress());
+        self::assertSame($log, $result);
+    }
+}