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

server/tsconfig.json

@@ -0,0 +1,22 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "declaration": true,
+    "removeComments": true,
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "allowSyntheticDefaultImports": true,
+    "target": "ES2021",
+    "sourceMap": true,
+    "rootDir": "./src",
+    "outDir": "./dist",
+    "skipLibCheck": true,
+    "strictNullChecks": false,
+    "noImplicitAny": false,
+    "strictBindCallApply": false,
+    "forceConsistentCasingInFileNames": false,
+    "noFallthroughCasesInSwitch": false,
+    "resolveJsonModule": true
+  },
+  "exclude": ["node_modules", "dist", "test"]
+}