feat: add Express API base structure

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/middlewares/error.middleware.ts

@@ -0,0 +1,33 @@
+import type { Request, Response, NextFunction } from 'express';
+
+export class AppError extends Error {
+  constructor(
+    public statusCode: number,
+    public message: string,
+    public isOperational = true
+  ) {
+    super(message);
+    Object.setPrototypeOf(this, AppError.prototype);
+  }
+}
+
+export function errorMiddleware(
+  err: Error,
+  req: Request,
+  res: Response,
+  next: NextFunction
+) {
+  if (err instanceof AppError) {
+    return res.status(err.statusCode).json({
+      status: 'error',
+      message: err.message,
+    });
+  }
+
+  console.error('Unhandled error:', err);
+
+  return res.status(500).json({
+    status: 'error',
+    message: 'Internal server error',
+  });
+}