feature: PR 1/8 — React + Vite scaffolding alongside Angular

[devin-ai-integration]

Summary

First of 8 PRs migrating this Angular 9 HN PWA to React. This one only stands React up next to Angular — no Angular code, config, or dependency is touched, so nothing regresses.

• vite.config.ts with root: 'src', so src/index.html, src/assets, src/manifest.json and src/favicon.ico resolve unchanged.
• src/index.html gains only <div id="root"> next to <app-root>. The <script type="module" src="/main.tsx"> tag is not committed to the HTML — Angular CLI processes index.html and chokes on a .tsx module script — so a tiny Vite transformIndexHtml plugin injects it at dev/build time instead.
• src/main.tsx mounts a placeholder App inside BrowserRouter; React sources live in src/react/ to avoid colliding with Angular's src/app/.
• Angular scripts (start, build) are untouched; React gets dev, build:react, typecheck:react.

Angular is pinned to typescript@~3.7.5, which cannot parse modern react-router-dom type declarations. Rather than hand-writing a shim module (which would need extending in every later PR and would mask real type errors), a second compiler is installed side-by-side via an npm alias and used only for the React config:

"typescript": "~3.7.5",                    // Angular, unchanged
"typescript5": "npm:typescript@^5.6.0",    // React typecheck only
"typecheck:react": "node node_modules/typescript5/bin/tsc -p tsconfig.react.json --noEmit"

Verified: npx vite build and npm run typecheck:react both pass.

Note: npm run build (Angular) fails on Node 20 with error:0308010C:digital envelope routines::unsupported — a pre-existing Node/OpenSSL incompatibility of the Angular 9 Webpack toolchain, present on master before this branch and unaffected by it.

Devin-Org: engineering

Link to Devin session: https://app.devin.ai/sessions/e6419ebe67ff4f749fe1573a8e26cd07
Requested by: @abboudp

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