feat: Add styling libraries and apply error page styling

[lornakelly]

Description

Apply the final visual styling to the error state UI once the component library and design approach are agreed.

As part of this, ensure the error UI aligns with the project’s styling foundations using Tailwind CSS v4 and incorporates lucide-react for clear, consistent iconography.

Motivation

Ensure error states are visually consistent with the rest of the editor and provide a clear, polished user experience, while aligning with the chosen styling approach and shared UI patterns across the project

Proposed Implementation

No response

Definition of Done

• Implementation: Fully implemented according to the Serverless Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.