feat(billing): add sales_leads and stripe_events tables

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/models/__init__.py

@@ -64,6 +64,8 @@ from .draft_template import DraftTemplate
 from .account_settings import AccountSettings
 from .oauth_identity import OAuthIdentity  # noqa: F401
 from .plan_billing import PlanBilling  # noqa: F401
+from .sales_lead import SalesLead  # noqa: F401
+from .stripe_event import StripeEvent  # noqa: F401
 
 __all__ = [
     "User",
@@ -142,4 +144,6 @@ __all__ = [
     "AccountSettings",
     "OAuthIdentity",
     "PlanBilling",
+    "SalesLead",
+    "StripeEvent",
 ]