Add Symfony payload mapping, fixtures, and QA tooling

server/src/Repository/SignalRepository.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Repository;
+
+use App\Entity\Signal;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<Signal>
+ */
+class SignalRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, Signal::class);
+    }
+
+    /**
+     * @return list<Signal>
+     */
+    public function findRecent(int $limit): array
+    {
+        return $this->createQueryBuilder('signal')
+            ->orderBy('signal.createdAt', 'DESC')
+            ->setMaxResults($limit)
+            ->getQuery()
+            ->getResult();
+    }
+
+    public function save(Signal $signal): void
+    {
+        $entityManager = $this->getEntityManager();
+        $entityManager->persist($signal);
+        $entityManager->flush();
+    }
+}