fix: nginx waits for estore healthcheck before starting

Nginx resolves upstream hostnames at boot time; if estore isn't
registered in Docker DNS yet it crashes in a restart loop.
Using service_healthy lets nginx wait until the Next.js app
passes its healthcheck before nginx attempts to start.

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

docker-compose.yml

@@ -9,8 +9,10 @@ services:
     volumes:
       - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
     depends_on:
-      - main-site
-      - estore
+      main-site:
+        condition: service_started
+      estore:
+        condition: service_healthy
     restart: always
 
   # ── Main website ─────────────────────────────────────────────────────────────