Migrate service build/runtime configuration to Java 25

[Copilot]

This updates the project from Java 11 to Java 25 so the service, toolchain, and CI all target the same runtime level. It also applies targeted Java language modernizations introduced by the migration recipe.

• Java 25 build target and toolchain

  • pom.xml now targets Java 25 (maven.compiler.release/target).
  • Maven plugins were aligned for Java 25 compatibility:
    • maven-compiler-plugin → 3.15.0
    • maven-surefire-plugin / maven-failsafe-plugin → 3.5.6
  • Added required test JVM --add-opens flags for newer JDK encapsulation behavior.

• CI runtime alignment

  • .github/workflows/ci.yml now provisions JDK 25 via actions/setup-java.

• Code-level Java modernization

  • Applied Java language updates in service/resource code (pattern matching for instanceof, switch expression, unused catch variable _) without changing endpoint behavior.

<!-- pom.xml -->
<maven.compiler.target>25</maven.compiler.target>
<maven.compiler.release>25</maven.compiler.release>

return switch (house) {
    case GRYFFINDOR -> "...";
    case HUFFLEPUFF -> "...";
    case RAVENCLAW -> "...";
    case SLYTHERIN -> "...";
    default -> "...";
};

Based on Moderne Prethink context, this migration was applied via OpenRewrite recipe execution (org.openrewrite.java.migrate.UpgradeToJava25) and repository-level updates.

This change was produced with Moderne CLI and Moderne Agent Tools (MCP), informed by Moderne Prethink context (dependencies, test gaps, project identity).