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,

app/modules/monitoring/services/audit_provider.py

@@ -0,0 +1,78 @@
+# app/modules/monitoring/services/audit_provider.py
+"""
+Audit provider implementation for the monitoring module.
+
+Provides database-backed audit logging using the AdminAuditLog model.
+This wraps the existing admin_audit_service functionality in the
+AuditProviderProtocol interface.
+"""
+
+import logging
+from typing import TYPE_CHECKING
+
+from sqlalchemy.orm import Session
+
+from app.modules.contracts.audit import AuditEvent, AuditProviderProtocol
+from app.modules.tenancy.models import AdminAuditLog
+
+if TYPE_CHECKING:
+    pass
+
+logger = logging.getLogger(__name__)
+
+
+class DatabaseAuditProvider:
+    """
+    Database-backed audit provider.
+
+    Logs admin actions to the AdminAuditLog table.
+    This is the default audit backend for the platform.
+    """
+
+    @property
+    def audit_backend(self) -> str:
+        return "database"
+
+    def log_action(self, db: Session, event: AuditEvent) -> bool:
+        """
+        Log an audit event to the database.
+
+        Args:
+            db: Database session
+            event: The audit event to log
+
+        Returns:
+            True if logged successfully, False otherwise
+        """
+        try:
+            audit_log = AdminAuditLog(
+                admin_user_id=event.admin_user_id,
+                action=event.action,
+                target_type=event.target_type,
+                target_id=str(event.target_id),
+                details=event.details or {},
+                ip_address=event.ip_address,
+                user_agent=event.user_agent,
+                request_id=event.request_id,
+            )
+
+            db.add(audit_log)
+            db.flush()
+
+            logger.debug(
+                f"Admin action logged: {event.action} on {event.target_type}:"
+                f"{event.target_id} by admin {event.admin_user_id}"
+            )
+
+            return True
+
+        except Exception as e:
+            logger.error(f"Failed to log admin action: {str(e)}")
+            # Don't raise exception - audit logging should not break operations
+            return False
+
+
+# Singleton instance
+audit_provider = DatabaseAuditProvider()
+
+__all__ = ["DatabaseAuditProvider", "audit_provider"]