Multi-Theme React UI Frontend

I’m developing a new web service and need a React-JS frontend that ships with three distinct, switchable themes. I already have the theme concepts defined; you’ll receive the palettes, typography rules, and a few layout references once we start, but I’m open to your suggestions on refining them for consistency and accessibility.

Scope
• Build a clean project scaffold (Vite, CRA, or Next—your call) with routing, state management, and code-splitting set up.
• Design reusable, custom components (buttons, forms, tables, modals, notifications, etc.) and wire them for easy prop-driven theming.
• Implement theme-based CSS styling—CSS Modules, Styled-Components, or another CSS-in-JS approach is fine as long as variables can be switched at runtime.
• Handle common UI actions gracefully: form validation, optimistic updates, responsive layout shifts, and basic error boundaries.
• Prepare concise documentation so another developer can extend or integrate the build.

Tech notes
React 18+, hooks everywhere. Typescript is a plus but not mandatory. I’ll provide REST/GraphQL endpoints; you only need to consume mock data for now and leave clear placeholders for real API calls later.

Deliverables
1. Source code in a private Git repository.
2. Fully-functional web ui that loads a given JSON input file and works based on that
3. Setup guide and component usage notes.

I value clean architecture, semantic markup, and clear commit history. Show me examples of past theme-based React work—screenshots or links to live apps are even better. If you’re confident shaping polished UI with flexible styling and clever component composition, let’s talk.