Fix .NET 8 Blazor CRUD Razor file generation

[MohamedFasulAshab]

Summary

Blazor CRUD scaffolding for .NET 8 completed successfully and reported that Razor files were added, but it did not create the expected CRUD pages.

The .NET 8 preprocessed template classes implemented the legacy Microsoft.DotNet.Scaffolding.Shared.T4Templating.ITextTransformation interface. The current text-templating pipeline expects Microsoft.DotNet.Scaffolding.TextTemplating.ITextTransformation.

Because these are different CLR interfaces, the template instance could not be cast to the expected type. Template execution was skipped, but the scaffolding operation still reported success.

Changes

• Updated the .NET 8 Create, Delete, Details, Edit, and Index Blazor CRUD template classes to implement the interface expected by the current text-templating pipeline.
• Updated TextTemplatingStep to log an actionable error and return failure when a template type does not implement the expected interface.
• Strengthened the .NET 8 Blazor CRUD integration test to verify:
  • The generated pages directory exists.
  • All five CRUD Razor files are generated.
  • The DbContext file is generated.
  • The project builds successfully after scaffolding.

Validation

• Built dotnet-scaffold for .NET 8.
• Ran the .NET 8 Blazor CRUD integration test.
• Verified generation of Create, Delete, Details, Edit, and Index Razor pages.
• Verified DbContext generation.
• Verified that the generated project builds successfully.
• Verified that the changes introduce no whitespace errors.

Compatibility

• No public API changes.
• No changes to the generated Razor content.
• Existing compatible templates continue to use the same execution path.
• Incompatible template implementations now fail explicitly instead of reporting false success.

Output Screenshots

Fixes #3813.

[haileymck]

happy to reapprove after merge conflicts are resolved