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/catalog/models/__init__.py

@@ -9,11 +9,11 @@ Usage:
 """
 
 from app.modules.catalog.models.product import Product
-from app.modules.catalog.models.product_translation import ProductTranslation
 from app.modules.catalog.models.product_media import ProductMedia
+from app.modules.catalog.models.product_translation import ProductTranslation
 
 __all__ = [
     "Product",
-    "ProductTranslation",
     "ProductMedia",
+    "ProductTranslation",
 ]

app/modules/catalog/models/product.py

@@ -114,6 +114,9 @@ class Product(Base, TimestampMixin):
     inventory_entries = relationship(
         "Inventory", back_populates="product", cascade="all, delete-orphan"
     )
+    media_associations = relationship(
+        "ProductMedia", back_populates="product", cascade="all, delete-orphan"
+    )
 
     # === CONSTRAINTS & INDEXES ===
     __table_args__ = (

app/modules/catalog/models/product_media.py

@@ -4,6 +4,11 @@ Product-Media association model.
 
 Links media files to products with usage type tracking
 (main image, gallery, variant images, etc.)
+
+This model lives in the catalog module because:
+- It's an association specific to products
+- Catalog owns the relationship between its products and media
+- CMS provides generic media storage, catalog defines how it uses media
 """
 
 from sqlalchemy import (
@@ -25,6 +30,8 @@ class ProductMedia(Base, TimestampMixin):
 
     Tracks which media files are used by which products,
     including the usage type (main image, gallery, variant, etc.)
+
+    This is catalog's association table - CMS doesn't need to know about it.
     """
 
     __tablename__ = "product_media"
@@ -52,8 +59,9 @@ class ProductMedia(Base, TimestampMixin):
     variant_id = Column(Integer)  # Reference to variant if applicable
 
     # Relationships
-    product = relationship("Product")
-    media = relationship("MediaFile", back_populates="product_associations")
+    product = relationship("Product", back_populates="media_associations")
+    # MediaFile is generic and doesn't know about ProductMedia
+    media = relationship("MediaFile", lazy="joined")
 
     __table_args__ = (
         UniqueConstraint(