refactor: fix architecture violations with provider patterns and dependency inversion

Major changes:
- Add AuditProvider protocol for cross-module audit logging
- Move customer order operations to orders module (dependency inversion)
- Add customer order metrics via MetricsProvider pattern
- Fix missing db parameter in get_admin_context() calls
- Move ProductMedia relationship to catalog module (proper ownership)
- Add marketplace breakdown stats to marketplace_widgets

New files:
- contracts/audit.py - AuditProviderProtocol
- core/services/audit_aggregator.py - Aggregates audit providers
- monitoring/services/audit_provider.py - Monitoring audit implementation
- orders/services/customer_order_service.py - Customer order operations
- orders/routes/api/vendor_customer_orders.py - Customer order endpoints
- catalog/services/product_media_service.py - Product media service
- Architecture documentation for patterns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/monitoring/definition.py

@@ -17,6 +17,13 @@ def _get_admin_router():
     return admin_router
 
 
+def _get_audit_provider():
+    """Lazy import of audit provider to avoid circular imports."""
+    from app.modules.monitoring.services.audit_provider import audit_provider
+
+    return audit_provider
+
+
 # Monitoring module definition
 monitoring_module = ModuleDefinition(
     code="monitoring",
@@ -112,6 +119,10 @@ monitoring_module = ModuleDefinition(
     is_core=False,
     is_internal=True,  # Internal module - admin-only, not customer-facing
     # =========================================================================
+    # Audit Provider
+    # =========================================================================
+    audit_provider=_get_audit_provider,
+    # =========================================================================
     # Self-Contained Module Configuration
     # =========================================================================
     is_self_contained=True,