Add error handling middleware for asyncHandler

[Aanand-code]

🚀 Added Error Handling Middleware

Problem

The asyncHandler catches errors and calls next(error), but there was no error handling middleware to actually send responses to the client.

Solution

1. Created middleware/errorMiddleware.js to handle errors from next(error)
2. Added the middleware to the Express app (must be last middleware)

Changes

• ✅ Added error handling middleware
• ✅ Proper error response formatting
• ✅ Support for both ApiError and unexpected errors
• ✅ Development/production environment handling

Testing

The middleware now properly handles:

• ApiError instances (structured errors)
• Unexpected errors (generic 500 responses)
• Development stack traces
• Production-safe error messages

[Aanand-code]

Adds error handling middleware to complete the asyncHandler flow. Now errors caught by asyncHandler properly return JSON responses instead of hanging.