feat: Full petmaster CRM with NestJS API and React frontend

- Client management (CRUD with JSONB custom fields)
- Pet profiles
- Service catalog with per-client pricing
- Booking calendar with recurring appointments
- Invoicing with Stripe integration
- Real-time messaging (WebSocket)
- Self-booking portal
- Staff assignment
- Docker multi-stage builds
- Prisma schema + seed

api/.env.example

@@ -0,0 +1,6 @@
+DATABASE_URL=postgresql://petmaster:petmaster_secret@postgres:5432/petmaster
+STRIPE_SECRET_KEY=sk_test_placeholder
+STRIPE_WEBHOOK_SECRET=whsec_placeholder
+JWT_SECRET=change-me-in-production
+CORS_ORIGIN=http://localhost:3001
+PORT=3000