Migrate Angular 9 Hacker News client to React 18

[devin-ai-integration]

Migrate Angular 9 Hacker News client to React 18

Summary

This PR performs a complete framework migration from Angular 9 to React 18 for the Hacker News client application. The migration includes:

Phase 1 - Foundation Setup:

• Replaced Angular bootstrap with React 18 entry point using Vite
• Converted App Component to React functional component with React Router v6
• Set up TypeScript configuration for React with strict mode
• Configured ESLint for React

Phase 2 - Core Feature Migration:

• Converted HackerNewsAPIService to React Query hooks (useHackerNews.ts)
• Converted SettingsService to React Context + custom hook pattern (SettingsContext.tsx)
• Migrated FeedComponent and ItemComponent to React functional components

Phase 3 - Advanced Features:

• Migrated ItemDetailsComponent, CommentComponent (with recursive rendering), and UserComponent
• Converted all CoreModule components (Header, Footer, Settings)
• Migrated shared components (Loader, ErrorMessage)

Phase 4 - PWA & Optimization:

• Replaced Angular Service Worker with Workbox via vite-plugin-pwa
• Implemented lazy loading with React.lazy() and Suspense
• Migrated all styles and themes (default, night, amoledblack)

Review & Testing Checklist for Human

This is a high-risk PR due to the complete framework rewrite. Please verify the following:

• Run the app locally (npm install && npm run dev) and verify the home page loads with news feed items
• Test all routes: /news/:page, /newest/:page, /show/:page, /ask/:page, /jobs/:page, /item/:id, /user/:id
• Test pagination - navigate between pages on feed views
• Test settings panel - verify theme switching (default/night/amoledblack), font size, and link behavior settings persist in localStorage
• Test item details - click on a story and verify comments render correctly with collapsible nested threads
• Verify PWA functionality - check that the app can be installed and works offline after initial load

Recommended test plan:

1. Run npm install && npm run dev
2. Open http://localhost:5173 in browser
3. Navigate through different feed types and pages
4. Click on a story to view details and comments
5. Open settings and change theme, verify it persists after refresh
6. Check browser DevTools Network tab for API calls to node-hnapi.herokuapp.com
7. Run npm run build to verify production build succeeds

Notes

• The build succeeds with SCSS deprecation warnings (expected for older Sass syntax)
• Original Angular tests were removed; no new tests were added in this migration
• The original E2E tests (Protractor) were removed; consider adding Cypress/Playwright tests as a follow-up

Link to Devin run: https://app.devin.ai/sessions/ce342de433804bf6a07c9cae9cc126a3
Requested by: Satwik Bebortha (satwik.bebortha@cognition.ai) / @satwik-cog

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