Enhance .NET Client to Match PHP Client's Capabilities

### Proposal:

Currently, the .NET client is just an auto-generated OpenAPI wrapper with poor developer experience. After using the PHP client, I'm impressed by its rich feature set and intuitive API design.

As a .NET developer, I'm requesting the community to help enhance the .NET client with similar functionality. The PHP client shows what's possible when you build a client manually with developer experience in mind, rather than relying on auto-generation.

**Key improvements needed for .NET:**
- Fluent query API (like PHP's `search()->filter()->sort()`)
- Better object modeling
- More intuitive configuration
- Comprehensive feature parity with PHP client

I'd love to contribute but need guidance from those familiar with the codebase. Are there any plans to improve the .NET client, or can the PHP maintainers share insights on building a proper .NET version?

The PHP client is excellent - let's bring that same quality to .NET!

### Checklist:

^{To be completed by the assignee. Check off tasks that have been completed or are not applicable.}

- [ ] Implementation completed
- [ ] Tests developed
- [ ] Documentation updated
- [ ] Documentation reviewed
- [x] OpenAPI YAML updated and issue created to rebuild clients