feat: implement tiered waitlist UI with Stripe checkout and webhooks

[SHEROSE0]

#closes #60

Summary

This PR introduces a responsive, tiered waitlist user interface integrated with Stripe Checkout sessions and backend webhook handling. It allows users to view different waitlist tiers, select a preferred tier, complete a secure payment, and handles the asynchronous status updates via webhooks.

Key Changes

• ✨ Tiered Waitlist UI: Created a polished, user-friendly frontend interface showcasing different waitlist priority tiers.
• 💳 Stripe Checkout Integration: Wired up the frontend to trigger secure Stripe Checkout sessions matching the selected tier.
• ⚡ Webhook Handling: Implemented webhook event listeners to securely catch successful payment events and update the user's waitlist status.
• 🔒 Environment Safety: Ensured .env.local and node_modules remain properly isolated, keeping the repository history clean.

How to Test

1. Pull this clean branch locally: git checkout feature/tiered-waitlist
2. Install any dependencies if prompted: npm install (or yarn install)
3. Ensure your local environment variables for Stripe are set up in your .env.local.
4. Run your local Stripe CLI webhook forwarder: stripe listen --forward-to localhost:YOUR_PORT/api/webhooks
5. Navigate to the waitlist page, select a tier, and complete a test transaction using Stripe test cards. Verify that the webhook captures the event and completes the flow.

Checklist

• Code follows the style guidelines of this project
• Checked for no accidental tracking of system or configuration files
• Tested webhook listeners locally

#closes

[SHEROSE0]

Hi maintainer please check this out.