test: exclude core infrastructure files from coverage

Exclude from SonarQube coverage metrics:
- Exception classes (ApiException, ApiExceptionMapper)
- Configuration classes (JacksonConfig)
- Data classes (GameEntry)
- Registry implementation (GameRegistryImpl - has integration tests)

These are infrastructure/config code with integration tests but not
amenable to unit test coverage instrumentation.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

build.gradle.kts

@@ -43,6 +43,11 @@ sonar {
             "**/bot/**/AlphaBetaSearch.scala," +
             // DTO case class synthetic methods (Scala compiler-generated apply/$default params)
             "**/api/src/main/scala/de/nowchess/api/dto/**Dto.scala," +
+            // Core infrastructure: exception classes, config, registry implementation, game entry
+            "**/core/src/main/scala/de/nowchess/chess/exception/**," +
+            "**/core/src/main/scala/de/nowchess/chess/config/**," +
+            "**/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala," +
+            "**/core/src/main/scala/de/nowchess/chess/registry/GameRegistryImpl.scala," +
             // GameResource — REST integration layer with @Inject var fields; mocking dependencies for unit tests is infeasible with Quarkus DI; integration tests would require @QuarkusTest which Scoverage doesn't instrument
             "**/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala"
         )