chore(repo): restructure as monorepo with server and client workspaces

- move NestJS app into server/ subdirectory
- add client/ React+TypeScript (Vite) app with Hello World
- update docker-compose to build and run both services
- add root package.json declaring npm workspaces
- update .gitignore to cover node_modules and dist at all depths

client/tsconfig.tsbuildinfo

@@ -0,0 +1 @@
+{"root":["./src/App.tsx","./src/main.tsx"],"version":"5.8.3"}