build: add NuGet lockfiles for dependency consistency

[dion-gionet]

Enables NuGet package lock files across all .NET projects in the repository to ensure consistent dependency resolution and reproducible builds.

Issue: DEVOPS-3973

[github-actions[bot]]

Let maintainers know that an action is required on their side

• Add the label https://github.com/Devolutions/devolutions-gateway/labels/release-required when you request a maintainer to cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module)

• Add the label https://github.com/Devolutions/devolutions-gateway/labels/release-blocker if a follow-up is required before cutting a new release

• Add the label https://github.com/Devolutions/devolutions-gateway/labels/publish-required when you request a maintainer to publish libraries (Devolutions.Gateway.Utils, OpenAPI clients, etc.)

• Add the label https://github.com/Devolutions/devolutions-gateway/labels/publish-blocker if a follow-up is required before publishing libraries

[CBenoit]

Thank you!

Please apply the PR guidelines: https://github.com/Devolutions/devolutions-gateway/blob/master/AGENTS.md#pull-request-guidelines

issue: We would use the build type for this kind of change.

note: I need to verify if this is fine for the auto-generated OpenAPI packages before merging.

[dion-gionet]

@CBenoit Fixed!