Add lightweight Blazor profile validation sample

[balajibashyam]

Summary

Adds a minimal .NET 10 companion sample for the Blazor .NET 8 Forms & Validation: EditForm, FluentValidation & Server Error Handling tutorial.

What's included

• New sample: blazor/forms-validation-masterclass/ — 16 files

  • Interactive Server Blazor Web App with manual EditContext
  • DataAnnotations validation on ProfileModel
  • Local FluentValidationBridge component (no archived adapter)
  • Whole-model validation on submit, property-specific on field change
  • Backend field-error mapping via ValidationMessageStore
  • Stale backend errors clear when the field is re-edited
  • Reusable FormTextField with aria-invalid and aria-describedby
  • Dirty-state detection with IsModified(), save/discard behavior
  • MarkAsUnmodified() after successful save
  • UseStatusCodePagesWithReExecute for custom 404
  • 8 bUnit component tests + 1 ASP.NET Core integration test

• Root README: New sample row + updated Blazor tree (both sample folders)

• GitHub Actions: New test-blazor-profile-validation job; path filters updated

Deliberately omitted (stays in the full tutorial)

• Archived Blazor FluentValidation adapters, async validation, API ProblemDetails, JavaScript focus, navigation guards, optimistic UI, authentication, databases, WebAssembly, Docker

Versions

• .NET SDK: 10.0.302
• FluentValidation.DependencyInjectionExtensions: 12.1.1
• bunit: 2.8.6
• Microsoft.AspNetCore.Mvc.Testing: 10.0.10
• xunit.v3: 3.2.2

Validation

• dotnet restore — passed
• dotnet build --configuration Release — passed (0 errors, 0 warnings)
• dotnet test --configuration Release — passed (9/9)
• HTTP GET / — 200 (seeded profile values rendered)
• HTTP GET /this-page-does-not-exist — 404 (custom Not Found page, no redirect)
• Security scan — clean