Validate, QA, and Polish Radzen-based UI Post-Migration

## Goal
Thoroughly test, refine, and polish the Elsa Studio UI after the Radzen Blazor migration is complete. Ensure visual and behavioral parity with the prior MudBlazor-based UI and that all modules function as intended in both Blazor Server and Wasm.

### Tasks
- Comprehensive QA pass (manual + automated) of all migrated modules/components.
- Regression, integration, and cross-browser testing.
- Review accessibility, dark/light themes, and overall UX consistency.
- Conduct stakeholder review and solicit feedback.
- Finalize with documentation updates and CI/CD config changes as needed.

#### Deliverables
- QA/test reports
- Polished UI
- Stakeholder approval
- Updated documentation and CI config

**Reference migration tracking checklists and audit outcomes for coverage assurance.**