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>

sonar-project.properties

@@ -4,3 +4,6 @@ sonar.sources=src,assets,templates
 sonar.exclusions=vendor/**,node_modules/**,public/build/**,var/**,migrations/**
 sonar.php.version=8.4
 sonar.sourceEncoding=UTF-8
+sonar.php.coverage.reportPaths=coverage.xml
+sonar.tests=tests
+sonar.test.inclusions=tests/**/*.php