feat(util): add ResourceClient for fluent resource operations

Add a utility class that provides fabric8-style fluent DSL for
Kubernetes resource operations. Features include:
- Fluent chaining: inNamespace(), withName(), withLabel()
- CRUD operations: get(), list(), create(), update(), delete()
- createOrReplace() for upsert semantics
- serverSideApply() integration
- waitUntilReady() and waitUntilCondition() support
- Immutable client instances for thread safety

Also adds comprehensive unit tests covering all operations,
fluent interface chaining, and error handling.

Author: brendandburns