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

docker-compose.yaml

@@ -1,7 +1,7 @@
 services:
-  app:
+  server:
     build:
-      context: .
+      context: ./server
       dockerfile: Dockerfile
     ports:
       - "13000:3000"
@@ -13,3 +13,11 @@ services:
       # mount key files into the container
       - ./keys:/app/keys
     restart: unless-stopped
+
+  client:
+    build:
+      context: .
+      dockerfile: client/Dockerfile
+    ports:
+      - "13001:80"
+    restart: unless-stopped