MBA-2260: Migrate angular2-hn from Angular to React

[devin-ai-integration]

Summary

Rebuilds the Hacker News PWA client in React (Vite + React 18 + TypeScript + react-router-dom v6), replacing the Angular 9 app in-place with full feature parity (MBA-2260).

Mapping of the Angular pieces:

• app.routes.ts → App.tsx routes: / → /news/1, five feed routes (/news|newest|show|ask|jobs/:page), lazy-loaded /item/:id and /user/:id (mirrors the Angular lazy modules).
• HackerNewsAPIService → src/services/api.ts: same node-hnapi.herokuapp.com endpoints, poll-option aggregation preserved (poll_votes_count), Observable cancel-token replaced with AbortController.
• SettingsService → SettingsContext: identical localStorage keys/defaults (theme, titleFontSize, listSpacing, openLinkInNewTab) and the same prefers-color-scheme behavior (system dark → night only when no saved theme).
• Components ported 1:1 (Header/Footer/Settings overlay, Feed/Item, ItemDetails with nested collapsible Comment tree and poll bars, User profile, Loader, skull ErrorMessage). All original SCSS kept, moved to src/styles/ with only selector-level adaptations (e.g. app-root:empty → #root:empty pre-boot loader).
• Angular service worker / ngsw-config.json → vite-plugin-pwa (Workbox): precached build assets, NetworkFirst runtime cache for the HN API, manifest values (name, icons, colors) carried over unchanged — offline support and installability maintained.
• Tests: Karma/Protractor replaced with Vitest + Testing Library (commentText, SettingsContext, api, Comment, Feed) and Playwright e2e (feed → item navigation, settings/theme switching) running against the built app via vite preview.

npm run lint, npm run test, npm run build, and npm run e2e all pass.

Devin-Org: engineering

Link to Devin session: https://app.devin.ai/sessions/0cd6012fc20043e6a844383c1371fee5
Open in Devin Desktop: https://app.devin.ai/desktop/session/0cd6012fc20043e6a844383c1371fee5?variant=devin

---

Devin Review

Status	Commit
⚪ Not started	—

Run Devin Review

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring