GetManyClients paging defaults are wrong and NextUrl double-counts #51

File: core/csharp/MicroZen.Api/Services/ClientsGrpcService.cs:30-47

What this is: Pagination in GetManyClients.

Problem: var page = request.Page > 0 ? request.Page : 10; treats Page as a page size, defaulting to 10 — but it is a page number everywhere else (NextUrl = page={request.Page + 1}). So Take(page) takes "page-number" rows, and Skip(skip) uses a raw Skip field that is never multiplied by page size. Paging returns overlapping/incorrect windows.

Fix: Separate page number from page size, compute Skip((page-1) * pageSize).Take(pageSize), and build NextUrl from the same variables.

If we skip it: Listing clients returns wrong, overlapping result pages.