v3.0: Upload actual api/main.py content

v3.0: Fix API - use shared modules, fix schema mismatch, add rate limiting, fix CORS

Upload api/main.py

Replace all clauseguard.com URLs with clauseguardweb.netlify.app

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