feat: update frontend training contents

[YadaYuki]

What

• Migration create-react-app -> Vite-based SPA
• Not changed main UI & Logic, just did some refactoring:
  • Integrate Linter & Formatter
  • Applied Lint & Format for all files 🙏🏻
  • Codebase organization ( migrated data fetching related logic to src/api/index.ts)
• Minor changed trainign materials
• Confirmed to work with [email protected], [email protected], and [email protected]

Why

• De facto deprecation of create-react-app 😢
  • Create React App Gone From React.dev, What happens to it now? facebook/create-react-app#13072
  • Replace Create React App recommendation with Vite reactjs/react.dev#5487
• When creating production-level applications, it is recommended to use frameworks like Next.js/Remix/GatsyBy/Astro.
• However, these frameworks involve too many considerations beyond UI implementation, such as hosting methods and rendering techniques (CSR/SSR/SSG), making them unsuitable for educational purposes in build education.
  → In Build training course, we decided to use Vite-based Simple SPA

CHECKS ⚠️

Please make sure you are aware of the following.

• **The changes in this PR doesn't have private information

[YadaYuki]

Added vscode recommended settings & extensions

[YadaYuki]

These deps are only for development, so migrated to devDeps

[YadaYuki]

Updated training materials 🙏🏻

[task4233]

Basically LGTM except for some imo/nits left comments.

[task4233]

LGTM
As I'm not super familiar with frontend code, I think it's better get review by the front end member as well.

[azrsh]

いくつか nit コメントしましたが基本良さそう
(nit コメントは対応しなくても問題ないです)