fix: load ngx_http_lua_module.so dynamic module in nginx.conf

libnginx-mod-http-lua is a dynamic module in Debian nginx; it must be
explicitly loaded with load_module or Lua directives are unrecognized.

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

docker/config/nginx/nginx.conf

@@ -1,4 +1,5 @@
 load_module modules/ngx_http_geoip2_module.so;
+load_module modules/ngx_http_lua_module.so;
 
 # Make POD_NAMESPACE and Redis URL available to Lua.
 env POD_NAMESPACE;