fix(docker): healthcheck uses 127.0.0.1, not localhost

In the alpine runtime 'localhost' resolves to ::1 (IPv6) first. The
SvelteKit Node adapter binds to 0.0.0.0 which is IPv4-only, so wget to
'localhost:3000' fails with 'Connection refused'. Traefik then filters
the container as unhealthy and no router is registered.

Using 127.0.0.1 makes the probe deterministically hit the bound IPv4
socket.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -34,6 +34,6 @@ VOLUME ["/data"]
 EXPOSE 3000
 
 HEALTHCHECK --interval=15s --timeout=5s --retries=3 --start-period=20s --start-interval=2s \
-  CMD wget -qO- http://localhost:3000/api/health > /dev/null || exit 1
+  CMD wget -qO- http://127.0.0.1:3000/api/health > /dev/null || exit 1
 
 CMD ["node", "build/index.js"]