[DEPS] Update Java to 25 LTS

[manusa]

Description

Update Java version from 21 to 25 LTS (latest Long Term Support release).

Context

Java 25 LTS provides:

• Performance improvements
• New language features
• Better GraalVM/Mandrel native image support
• Access to Mandrel 24.x+ builder images (which dropped Java 21 support)

Files to modify

• pom.xml - Update maven.compiler.source, maven.compiler.target, and maven.compiler.release properties
• src/main/docker/Dockerfile.build - Update Mandrel builder image
• .github/workflows/*.yml - Update Java version in CI workflows
• CLAUDE.md - Update Java version references

Dependencies

This should be done after:

• [DEPS] Update Quarkus to 3.30.3 #146 - Update Quarkus to 3.30.3
• [BREAKING] Migrate Fabric8 Kubernetes Client to 7.x #149 - Migrate Fabric8 Kubernetes Client to 7.x

Acceptance Criteria

• Project compiles and runs with Java 25
• All tests pass
• Native image builds successfully
• CI pipelines updated and passing

References

• Closes the gap that prevented [INFRA] Update Docker base images #151 from being implemented