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

.dockerignore

@@ -1,7 +0,0 @@
-node_modules
-dist
-data
-keys
-.env
-.git
-*.log