Fix backend TypeScript build errors

- Inline tsconfig.base.json settings into backend/tsconfig.json so the
  Docker build (which only copies backend/) can resolve them
- Replace default imports of Node built-ins (crypto, net) with named imports
- Replace default bcrypt import with named imports (compare, hash)
- Switch @fastify/websocket from v8 to v7 (SocketStream API) to match
  Fastify v4 peer dependency; update WebSocket handler signatures accordingly
- Remove obsolete `version` key from docker-compose.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/package.json

@@ -15,7 +15,7 @@
   "dependencies": {
     "@fastify/cors": "^9.0.1",
     "@fastify/jwt": "^8.0.1",
-    "@fastify/websocket": "^8.3.1",
+    "@fastify/websocket": "^7.2.0",
     "@prisma/client": "^5.17.0",
     "bcryptjs": "^2.4.3",
     "fastify": "^4.28.1",