feat: add marketplace metrics, privacy features, and service registry endpoints

- Add Prometheus metrics for marketplace API throughput and error rates with new dashboard panels
- Implement confidential transaction models with encryption support and access control
- Add key management system with registration, rotation, and audit logging
- Create services and registry routers for service discovery and management
- Integrate ZK proof generation for privacy-preserving receipts
- Add metrics instru

enterprise-connectors/python-sdk/aitbc_enterprise/payments/__init__.py

@@ -0,0 +1,19 @@
+"""
+Payment processor connectors for AITBC Enterprise
+"""
+
+from .base import PaymentConnector, PaymentMethod, Charge, Refund, Subscription
+from .stripe import StripeConnector
+from .paypal import PayPalConnector
+from .square import SquareConnector
+
+__all__ = [
+    "PaymentConnector",
+    "PaymentMethod",
+    "Charge",
+    "Refund",
+    "Subscription",
+    "StripeConnector",
+    "PayPalConnector",
+    "SquareConnector",
+]