0548a08cbb
Add Stripe payment integration across the project: - Add @stripe/stripe-js dependency - Configure Stripe environment variables (secret key, publishable key, webhook secret) for dev, local, and production environments - Add Product/Price IDs for monthly, quarterly, and annual subscription tiers - Extend subscription plan data with voiceMinutesPerDay quotas (30/45/60 minutes per tier) - Update .gitignore to exclude implementation_plan.md