fix: Update nginx config to use dynamic DNS resolution

- Replace upstream blocks with resolver directive
- Use variables for backend addresses to avoid startup errors
- Simplify configuration with single server block
- Add health check endpoint

server/api/node_modules/isarray/index.js

@@ -0,0 +1,5 @@
+var toString = {}.toString;
+
+module.exports = Array.isArray || function (arr) {
+  return toString.call(arr) == '[object Array]';
+};