fix: Use TCP port check for NATS healthcheck

NATS image has no wget/curl. Use bash TCP check on port 4222 instead.

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

docker/docker-compose.yml

@@ -29,10 +29,11 @@ services:
     ports:
       - "8089:4222"   # Client connections
     healthcheck:
-      test: ["CMD-SHELL", "wget -qO- http://localhost:8222/healthz || exit 1"]
+      test: ["CMD-SHELL", "echo > /dev/tcp/localhost/4222 || exit 1"]
       interval: 5s
-      timeout: 5s
+      timeout: 3s
       retries: 5
+      start_period: 5s
 
   api:
     build: