CONFIG: Update NuGet dependencies and modernise ADotNet build/PR workflows

[perirrs]

Summary

Brings CsvHelperClient up to the .NET 10 modernisation standard.

closes AB#29736

Dependency updates (CONFIG)

• Microsoft.Extensions.DependencyInjection 10.0.8 -> 10.0.9
• Microsoft.Extensions.Configuration 10.0.8 -> 10.0.9
• Microsoft.Extensions.Configuration.Json 10.0.8 -> 10.0.9
• Microsoft.NET.Test.Sdk 18.5.1 -> 18.7.0
• ADotNet 4.3.0 -> 5.0.0
• dependabot: add FluentAssertions ignore rule (locked at [7.2.2])

Workflow modernisation (CODE RUB)

• ADotNet components -> latest (CheckoutTaskV5 / SetupDotNetTaskV5 / LabelJobV3 / TagJobV2 / PublishJobV4); build.yml now on Node-24 actions (checkout@v5, setup-dotnet@v5, github-script@v8)
• Added prLinter.yml (Label, Require Issue Or Task, Set Author As PR Assignee, branch-filtered); moved the label job out of build.yml
• Fixed build job-id casing (Build -> build) to match the needs: reference

Validation

• Build: 0 errors, 0 obsolete warnings
• Tests: 38 pass (9 Acceptance + 29 Unit)
• Vulnerable packages: none
• Workflows regenerated from the Infrastructure project (not hand-edited), idempotent