Add fuzzing testing with CATS

[jabrena]

User Story

As a maintainer of cursor-rules-java, I want to add a new fuzz-testing skill named 134-java-testing-fuzzing-testing using CATS so that we can automatically discover contract and edge-case failures in our APIs before release.

Context

• CATS project: https://github.com/Endava/cats
• New skill identifier: 134-java-testing-fuzzing-testing

Acceptance Criteria

• Given the project build pipeline, when fuzz tests run with CATS, then failures are reported in CI with reproducible request/response details.
• Given existing API contracts/examples, when CATS executes negative and boundary test scenarios, then invalid inputs are validated and handled with expected error responses.
• Given a contributor onboarding to this feature, when they read project docs, then they can run CATS checks locally with clear setup and execution steps.
• Given implementation planning and documentation, when the new skill is referenced, then the identifier used is 134-java-testing-fuzzing-testing.

[jabrena]

#634