v4.0: Update .env.example with all required env vars

Replace Stripe with Razorpay: subscriptions, webhooks, checkout modal, INR pricing

v3: All missing features — auth callback, settings, PDF export, email (Resend), JWT auth, /api/history, SaulLM integration, extension icons, Supabase 0.10 breaking changes, Stripe v22

🛡️ ClauseGuard v1.0 — Full codebase: Extension + Website + API + ML