Integrate Storybook for React UI components

[code-by-sia]

Summary

• Adds Storybook with the React/Vite framework and docs addon.
• Adds scripts for local Storybook development and static Storybook builds.
• Adds initial stories for shared UI primitives and the ribbon menu.
• Documents the Storybook workflow in README and the development guide.
• Ignores generated storybook-static/ output and regenerates app build assets.

Closes #59.

Verification

• npm test
• npm run typecheck
• npm run build
• npm run build-storybook

Notes:

• npm run build still reports the existing direct eval warning in src/lib/core/formula/Evaluator.ts; build succeeds.
• npm run build-storybook reports large Storybook bundle chunks; the static Storybook build succeeds.