fix: import styled-components named export

[simPod]

Summary

• replace default styled-components imports with named styled imports
• fixes native ESM/SSR consumers where import styled from 'styled-components' resolves to a CJS namespace object without .div, .svg, etc.
• add jest-util as an explicit dev dependency to satisfy ts-jest's peer dependency and keep npm test working from a clean install

Verification

• npm ci
• npm run typecheck
• npm test
• npm run build
• node --input-type=module -e \"const spinner = await import('./dist/index.mjs'); console.log(typeof spinner.Oval); const oval = await import('./dist/oval.mjs'); console.log(typeof oval.Oval);\"
• node -e \"const spinner = require('./dist/index.cjs'); console.log(typeof spinner.Oval);\"