fix: Docker healthcheck IPv6 connection refused

Changed healthcheck from localhost to 127.0.0.1 to force IPv4 connection.
The issue occurred because 'localhost' resolves to IPv6 (::1) but nginx
only listens on IPv4 by default, causing healthchecks to fail.

Error before fix:
  Connecting to localhost ([::1]:80)
  wget: can't connect to remote host: Connection refused

Updated both Dockerfile and docker-compose.yml for consistency.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.yml

@@ -11,7 +11,7 @@ services:
       - "80:80"
     restart: unless-stopped
     healthcheck:
-      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost/"]
+      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://127.0.0.1/"]
       interval: 30s
       timeout: 10s
       retries: 3