How to Add Subscription Billing to Your Lovable App

# Stripe Dashboard → Products → + Add Product
# Name: Pro Plan
# Pricing: Recurring → $29/month
# Copy the price_id (starts with price_)

Create a Supabase Edge Function called 'create-subscription' that:
1. Accepts price_id and user_email in the request body
2. Creates or retrieves a Stripe customer by email
3. Creates a Checkout session with mode: 'subscription'
4. Sets success_url and cancel_url
5. Returns the checkout URL
6. Uses STRIPE_SECRET_KEY from env

Create a /pricing page with two plan cards side by side:
1. Free plan: list basic features, 'Current Plan' badge if user is free
2. Pro plan ($29/mo): list premium features, 'Upgrade' button that calls create-subscription
3. If user is already Pro, show 'Manage Subscription' button instead
4. Modern, clean design with the Pro card highlighted

Create a Supabase Edge Function called 'subscription-webhook' that handles:
1. checkout.session.completed → set user subscription_status to 'active'
2. customer.subscription.updated → update plan details
3. customer.subscription.deleted → set subscription_status to 'cancelled'
4. Verify webhook signature with STRIPE_WEBHOOK_SECRET
5. Update the subscriptions table in the database

Add a 'Manage Subscription' button on the settings page that:
1. Calls a new Edge Function 'create-portal-session'
2. The function creates a Stripe Billing Portal session
3. Redirects the user to the Stripe portal
4. They can update payment, change plan, or cancel

Create a useSubscription hook that:
1. Checks the current user's subscription_status in the database
2. Returns { isPro, isLoading }
3. Use this hook to show/hide Pro features across the app
4. Show an 'Upgrade to Pro' prompt when free users try Pro features