Jerxpert Payment & Subscription Integration

I’ve already launched Jerxpert, a site where visitors explore and use various AI tools, but the payment layer is still missing. I need a developer who can weave in a smooth, reliable system for paid access—think subscription tiers, one-off credits, and usage limits that lock or unlock specific tools automatically.

Here’s the situation:
• The core site is up and running.
• Users can browse and test the AI tools, but everything is free right now.
• I want to introduce paid plans (monthly, annual, or pay-as-you-go) and ensure usage tracking so heavy users don’t exceed their quota without upgrading.

Key tasks I’d like you to tackle:
1. Integrate a mainstream gateway such as Stripe or PayPal for card payments, webhooks, and secure storage of customer data.
2. Create subscription logic—free trial, tiered plans, coupon handling, and automatic renewal/cancellation.
3. Build a usage meter that checks each call to an AI tool against the user’s allowance and responds accordingly.
4. Surface this information in a lightweight account dashboard so users always know their current plan and remaining quota.
5. Test the full flow end-to-end (signup → choose plan → pay → use tools → hit limits → upgrade or renew).

Acceptance criteria
• A new user can sign up, choose a plan, pay, and immediately gain the right features or usage limits.
• Exceeding a quota triggers the correct upgrade prompt or lockout.
• Admin view reports real-time revenue and individual usage data.
• No security warnings or payment errors in production mode.

Tech stack flexibility: the back-end is fairly standard (Node.js + Express) with a React front-end, but I’m open to your preferred libraries if they mesh well. Please outline your proposed approach, timeline, and any similar integrations you’ve shipped before.