fix: Replace socket.io with native WS adapter — fixes WebSocket 1006

Frontend uses native WebSocket API, backend was using socket.io which
speaks an incompatible protocol. Switched to @nestjs/platform-ws so
both sides speak native WebSocket. Also fixed JWT TTL override in
docker-compose.yml (was hardcoded to 900s, now 14400s/4h).

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

docker/docker-compose.yml

@@ -37,7 +37,7 @@ services:
       DATABASE_MAX_CONNECTIONS: "20"
       NATS_URL: nats://nats:4222
       JWT_SECRET: ${JWT_SECRET}
-      JWT_ACCESS_EXPIRY_SECONDS: "900"
+      JWT_ACCESS_EXPIRY_SECONDS: "14400"
       JWT_REFRESH_EXPIRY_SECONDS: "604800"
       ENCRYPTION_KEY: ${ENCRYPTION_KEY}
       CLOUDFLARE_API_TOKEN: ${CLOUDFLARE_API_TOKEN}