chore(angular-react): Migrate Conduit to React + TypeScript + Vite (parallel rewrite)

[devin-ai-integration]

Summary

Parallel React + TypeScript + Vite rewrite of the Angular Conduit app, living entirely in a new react-app/ subdirectory. The Angular source under src/ is untouched — this adds a second, independent frontend that talks to the same RealWorld API (https://api.realworld.show/api) with identical data contracts, routes/URLs, and styling.

Why: groundwork to evaluate/move off Angular without disrupting the existing app or its e2e/CI.

What was ported (1:1, no behavior changes)

• Core / auth — Angular interceptors + UserService collapse into a small fetch wrapper + an AuthProvider context:
  • apiClient prepends the API root, injects Authorization: Token <jwt> (token in localStorage['jwtToken']), and globally purges auth on a 401 for any endpoint except /user (the old errorInterceptor).
  • AuthContext reproduces the auth state machine loading → authenticated | unauthenticated | unavailable, including the startup getCurrentUser() initializer, 4XX→logout vs 5XX→retry distinction, and exponential backoff (2,4,8,16,16s).
  • window.__conduit_debug__ is re-exposed for the e2e debug helpers.
• Services / models — articles, comments, tags, profile, user and all interfaces (User, Profile, Article, Comment, ArticleListConfig, ...).
• Routing — same URLs via React Router (/, /tag/:tag, /login, /register, /settings, /profile/:username (+ /favorites nested), /editor, /editor/:slug, /article/:slug), with ?feed=following / ?page=N query params and route guards.
• Components / pages — Header, Footer, ListErrors, ArticleList (pagination), ArticlePreview, ArticleMeta, FollowButton, FavoriteButton, ArticleComment; Home, Auth, Article, Editor, Profile (+ Articles/Favorites), Settings.
• Pipes → utils — MarkdownPipe → marked + DOMPurify; DefaultImagePipe → defaultImage(); Angular date pipes → Intl.DateTimeFormat.
• Styling/assets — copied RealWorld styles.css, conduit-logo.svg, default-avatar.svg into react-app/. (Original app is not a PWA — nothing to port there.)

Lifecycle mapping, e.g. the ArticleList query:

ngOnInit + @Input changes  ->  useEffect([JSON.stringify(config), page, limit])
@Output pageChange         ->  props.onPageChange(page)

Repo-level change

• Added a root .prettierignore (react-app/dist, react-app/package-lock.json, node_modules) so the existing format:check CI job ignores generated React output. All committed react-app sources are Prettier-clean.

Verification

• cd react-app && npm run build → 0 TypeScript errors; npm run lint → 0 errors (1 non-blocking react-refresh warning); repo bun run format:check passes.
• Manually exercised against the live API on localhost:4200: register/login/logout, create article (markdown + tags), comment, favorite (count updates), follow, tag filter, profile tabs, settings prefill + update + error display.

Link to Devin session: https://app.devin.ai/sessions/eb3cec2ca42643a9a3a780ab08132089
Requested by: @lburgers

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