Add PHPUnit tests with coverage for all src classes

- 21 test files covering controllers, services, entities, enums, messages
- CI: add test job with Xdebug coverage (clover + text)
- SonarQube: configure coverage report path and test sources

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

tests/Message/MeilisearchMessageTest.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Tests\Message;
+
+use App\Message\MeilisearchMessage;
+use PHPUnit\Framework\TestCase;
+
+class MeilisearchMessageTest extends TestCase
+{
+    public function testConstructorSetsProperties(): void
+    {
+        $message = new MeilisearchMessage('addDocuments', 'events', ['documents' => [['id' => 1]]]);
+
+        self::assertSame('addDocuments', $message->action);
+        self::assertSame('events', $message->index);
+        self::assertSame(['documents' => [['id' => 1]]], $message->payload);
+    }
+
+    public function testDefaultPayloadIsEmpty(): void
+    {
+        $message = new MeilisearchMessage('deleteIndex', 'events');
+
+        self::assertSame([], $message->payload);
+    }
+}