Add frontend foundation

[KevinMehrabi]

Summary

• add a standalone React, Vite, and TypeScript frontend under frontend/
• establish the approved typography, color, spacing, accessibility, and reduced-motion foundations
• introduce exact atomic-amount and asset-identifier primitives without JavaScript number conversion
• add a dedicated frontend verification workflow

Scope

This foundation is isolated from the existing protocol work. It does not change contracts, deployment scripts, src/util, or the legacy src/ui application. It contains no RPC access, wallet integration, Taquito operations, contract addresses, network manifests, or mainnet path. The approved fixture dashboard will follow in a separate interface PR.

Verification

• npm run typecheck
• npm test — 13 tests passed
• npm run build
• npm audit --audit-level=high — 0 vulnerabilities
• npm audit --omit=dev --audit-level=high — 0 vulnerabilities