refactor: migrate templates and static files to self-contained modules

Templates Migration:
- Migrate admin templates to modules (tenancy, billing, monitoring, marketplace, etc.)
- Migrate vendor templates to modules (tenancy, billing, orders, messaging, etc.)
- Migrate storefront templates to modules (catalog, customers, orders, cart, checkout, cms)
- Migrate public templates to modules (billing, marketplace, cms)
- Keep shared templates in app/templates/ (base.html, errors/, partials/, macros/)
- Migrate letzshop partials to marketplace module

Static Files Migration:
- Migrate admin JS to modules: tenancy (23 files), core (5 files), monitoring (1 file)
- Migrate vendor JS to modules: tenancy (4 files), core (2 files)
- Migrate shared JS: vendor-selector.js to core, media-picker.js to cms
- Migrate storefront JS: storefront-layout.js to core
- Keep framework JS in static/ (api-client, utils, money, icons, log-config, lib/)
- Update all template references to use module_static paths

Naming Consistency:
- Rename static/platform/ to static/public/
- Rename app/templates/platform/ to app/templates/public/
- Update all extends and static references

Documentation:
- Update module-system.md with shared templates documentation
- Update frontend-structure.md with new module JS organization

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

app/modules/catalog/exceptions.py

@@ -2,7 +2,10 @@
 """
 Catalog module exceptions.
 
-Module-specific exceptions for product catalog operations.
+This module provides exception classes for catalog operations including:
+- Product management (CRUD)
+- Product validation
+- Product dependencies (inventory, orders)
 """
 
 from app.exceptions.base import (
@@ -12,6 +15,19 @@ from app.exceptions.base import (
     ValidationException,
 )
 
+__all__ = [
+    "ProductNotFoundException",
+    "ProductAlreadyExistsException",
+    "ProductNotInCatalogException",
+    "ProductNotActiveException",
+    "InvalidProductDataException",
+    "ProductValidationException",
+    "CannotDeleteProductException",
+    "CannotDeleteProductWithInventoryException",
+    "CannotDeleteProductWithOrdersException",
+    "ProductMediaException",
+]
+
 
 class ProductNotFoundException(ResourceNotFoundException):
     """Raised when a product is not found in vendor catalog."""
@@ -56,11 +72,9 @@ class ProductNotInCatalogException(ResourceNotFoundException):
             identifier=str(product_id),
             message=f"Product {product_id} is not in vendor {vendor_id} catalog",
             error_code="PRODUCT_NOT_IN_CATALOG",
-            details={
-                "product_id": product_id,
-                "vendor_id": vendor_id,
-            },
         )
+        self.details["product_id"] = product_id
+        self.details["vendor_id"] = vendor_id
 
 
 class ProductNotActiveException(BusinessLogicException):
@@ -77,6 +91,23 @@ class ProductNotActiveException(BusinessLogicException):
         )
 
 
+class InvalidProductDataException(ValidationException):
+    """Raised when product data is invalid."""
+
+    def __init__(
+        self,
+        message: str = "Invalid product data",
+        field: str | None = None,
+        details: dict | None = None,
+    ):
+        super().__init__(
+            message=message,
+            field=field,
+            details=details,
+        )
+        self.error_code = "INVALID_PRODUCT_DATA"
+
+
 class ProductValidationException(ValidationException):
     """Raised when product data validation fails."""
 
@@ -109,6 +140,34 @@ class CannotDeleteProductException(BusinessLogicException):
         )
 
 
+class CannotDeleteProductWithInventoryException(BusinessLogicException):
+    """Raised when trying to delete a product that has inventory."""
+
+    def __init__(self, product_id: int, inventory_count: int):
+        super().__init__(
+            message=f"Cannot delete product {product_id} - it has {inventory_count} inventory entries",
+            error_code="CANNOT_DELETE_PRODUCT_WITH_INVENTORY",
+            details={
+                "product_id": product_id,
+                "inventory_count": inventory_count,
+            },
+        )
+
+
+class CannotDeleteProductWithOrdersException(BusinessLogicException):
+    """Raised when trying to delete a product that has been ordered."""
+
+    def __init__(self, product_id: int, order_count: int):
+        super().__init__(
+            message=f"Cannot delete product {product_id} - it has {order_count} associated orders",
+            error_code="CANNOT_DELETE_PRODUCT_WITH_ORDERS",
+            details={
+                "product_id": product_id,
+                "order_count": order_count,
+            },
+        )
+
+
 class ProductMediaException(BusinessLogicException):
     """Raised when there's an issue with product media."""
 
@@ -118,14 +177,3 @@ class ProductMediaException(BusinessLogicException):
             error_code="PRODUCT_MEDIA_ERROR",
             details={"product_id": product_id},
         )
-
-
-__all__ = [
-    "CannotDeleteProductException",
-    "ProductAlreadyExistsException",
-    "ProductMediaException",
-    "ProductNotActiveException",
-    "ProductNotFoundException",
-    "ProductNotInCatalogException",
-    "ProductValidationException",
-]