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/Enum/CacheKeyTest.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Tests\Enum;
+
+use App\Enum\CacheKey;
+use PHPUnit\Framework\TestCase;
+
+class CacheKeyTest extends TestCase
+{
+    public function testResolveWithParameters(): void
+    {
+        self::assertSame('user_profile_42', CacheKey::USER_PROFILE->resolve(42));
+        self::assertSame('event_detail_10', CacheKey::EVENT_DETAIL->resolve(10));
+        self::assertSame('search_symfony', CacheKey::SEARCH_RESULTS->resolve('symfony'));
+    }
+
+    public function testResolveWithoutParameters(): void
+    {
+        self::assertSame('event_list', CacheKey::EVENT_LIST->resolve());
+        self::assertSame('home_page', CacheKey::HOME_PAGE->resolve());
+    }
+
+    public function testTtlReturnsPositiveIntegers(): void
+    {
+        foreach (CacheKey::cases() as $case) {
+            self::assertGreaterThan(0, $case->ttl(), "TTL for {$case->name} should be positive");
+        }
+    }
+
+    public function testSpecificTtlValues(): void
+    {
+        self::assertSame(1800, CacheKey::USER_PROFILE->ttl());
+        self::assertSame(300, CacheKey::EVENT_LIST->ttl());
+        self::assertSame(60, CacheKey::EVENT_TICKETS->ttl());
+        self::assertSame(3600, CacheKey::SITEMAP_MAIN->ttl());
+    }
+}