Incrementally Migrate Layout, Theming, and Modules from MudBlazor to Radzen

## Goal
Incrementally transition Elsa Studio UI towards Radzen Blazor, first converting core layout/theming and shared UI shells, followed by module-level work. This ensures central app functionality is preserved and migration is parallelizable.

### Phases
#### Phase 1: Core Layout & Theming
- [ ] Migrate `BasicLayout.razor` ([src/framework/Elsa.Studio.Shared/Layouts/BasicLayout.razor](https://github.com/elsa-workflows/elsa-studio/blob/main/src/framework/Elsa.Studio.Shared/Layouts/BasicLayout.razor)) and `MainLayout.razor` & `.razor.cs` ([src/framework/Elsa.Studio.Shared/Layouts/MainLayout.razor](https://github.com/elsa-workflows/elsa-studio/blob/main/src/framework/Elsa.Studio.Shared/Layouts/MainLayout.razor)), including theme providers, snackbar, dialog, and popover logic.
- [ ] Update all hosts to use Radzen providers and CSS/JS (see host files in audit issue for links).

#### Phase 2: Module/Component Migration
- For each module below:
- Remove MudBlazor/MudExtensions from `_Imports.razor`, individual components, and view models.
- Replace with Radzen equivalents, update imports/usings and member types.
- Migrate themes, layout references, and styles.

- [ ] `Elsa.Studio.UIHints`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.UIHints)
- [ ] `Elsa.Studio.Workflows.Designer`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Workflows.Designer)
- [ ] `Elsa.Studio.Login`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Login)
- [ ] `Elsa.Studio.Localization`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Localization)
- [ ] `Elsa.Studio.Security`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Security)
- [ ] `Elsa.Studio.Counter`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Counter)
- [ ] `Elsa.Studio.Dashboard`: [Module Link](https://github.com/elsa-workflows/elsa-studio/tree/main/src/modules/Elsa.Studio.Dashboard)

(Adjust breakdown as needed based on sub-component audits. Include references to key components in each module.)

#### Deliverables
- PRs per phased migration
- Status documentation per module
- References to updated files in checklists