Fix nginx: use TCP socket (127.0.0.1:9000) matching php-fpm default

The php:8.4-fpm-alpine image listens on TCP by default, not unix socket.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/nginx/default.conf

@@ -15,7 +15,7 @@ server {
     }
 
     location ~ \.php$ {
-        fastcgi_pass unix:/var/run/php-fpm.sock;
+        fastcgi_pass 127.0.0.1:9000;
         fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
         include fastcgi_params;
         fastcgi_read_timeout 60s;