Fix Meta WhatsApp API Integration

My Node.js backend and React SaaS dashboard are ready, but the official Meta WhatsApp Business API layer is still unstable. Two pain points block us from launch:

1. Embedded Signup
The “Login with Facebook” flow stalls midway, so customers cannot onboard their own WABA numbers. I need that client-side flow repaired, tested, and proven to complete without manual intervention.

2. Meta App & Webhooks
Current symptoms point to incorrect app configuration and a webhook endpoint that never receives callbacks. Once you straighten out the App ID, System User, long-lived access tokens, and required scopes (whatsapp_business_management & whatsapp_business_messaging), the webhook endpoint must reliably accept and log every event we subscribe to.

Deliverables
• Working embedded signup that adds a customer’s number and sends the first template message from our interface.
• Clean Meta App configuration committed to our vault (.env / secrets manager) with updated docs describing each step.
• Stable HTTPS webhook endpoint (Express) that captures sample events and returns 200 OK to Meta, with logging visible in the React admin panel.
• Short hand-off note: commands to spin up the feature branch locally, plus Postman collection or curl scripts to demo success.

Stack highlights: Node.js, Express, React, MongoDB, Meta Graph API, WhatsApp Cloud API, Webhooks.

I’ll give you Git access and a Meta developer account sandbox as soon as we agree. Let’s get the integration solid and ready for production rollout.