Add async/non-blocking request handling

[devondragon]

Currently all requests are synchronous. This issue proposes adding asynchronous request handling for better performance.

Proposed Changes

• Implement async versions of all service methods
• Add support for CompletableFuture, Mono/Flux for reactive applications
• Create examples showing async usage patterns
• Ensure proper error handling in async contexts

Benefits

• Improves application performance for multiple requests
• Supports reactive programming models
• Better handles high-throughput scenarios