Fix code review feedback: API typo, null safety, duplicate property, docs

[Copilot]

• Fix redundant properties in DomainUpdateV2.cs (removed AutoRenewEnabled, kept RenewAuto for consistency)
• Fix typo in Client.Agreements.cs (aggreements -> agreements)
• Add null check in QueryStringBuilder.cs for dictionary values
• Update documentation comment in Services.cs to be more accurate
• Test changes to ensure no regressions (code review and security scan passed)
• Add V1_BASE and V2_BASE constants to Client.cs to fix build errors

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[ahwm]

@copilot Fix build errors by adding the V2_BASE constant to Client.cs (it was previously in Client.DomainV2.cs) as described here

[Copilot]

@copilot Fix build errors by adding the V2_BASE constant to Client.cs (it was previously in Client.DomainV2.cs) as described [here](#87 (comment)...

Fixed in commit 863d15d. I've added both V1_BASE and V2_BASE constants to Client.cs and removed the duplicate V1_BASE from Client.Domain.cs. This makes both constants accessible to all partial classes.

The solution now builds successfully with 0 errors and 0 warnings across all target frameworks (.NET 4.6.2, .NET Standard 2.0, .NET 8, .NET 10).