feat : add Client entity with CRUD API

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Repository/ClientRepository.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Repository;
+
+use App\Entity\Client;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+class ClientRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, Client::class);
+    }
+}