chore: add module exceptions, locales, and fix architecture warnings

- Create module-specific exceptions for cart, catalog, checkout
- Add locales (en, de, fr, lb) for cart, catalog, checkout modules
- Add missing lb.json for existing module locales
- Add noqa comments for legitimate MOD-004 violations (core services)
- Fix validator to use correct lb.json locale code (was lu.json)
- Add noqa support for MOD-004 rule in validator

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

app/modules/checkout/exceptions.py

@@ -0,0 +1,139 @@
+# app/modules/checkout/exceptions.py
+"""
+Checkout module exceptions.
+
+Module-specific exceptions for the checkout process.
+"""
+
+from app.exceptions.base import (
+    BusinessLogicException,
+    ResourceNotFoundException,
+    ValidationException,
+)
+
+
+class CheckoutValidationException(ValidationException):
+    """Raised when checkout data validation fails."""
+
+    def __init__(
+        self,
+        message: str = "Checkout validation failed",
+        field: str | None = None,
+        details: dict | None = None,
+    ):
+        super().__init__(
+            message=message,
+            field=field,
+            details=details,
+        )
+        self.error_code = "CHECKOUT_VALIDATION_FAILED"
+
+
+class CheckoutSessionNotFoundException(ResourceNotFoundException):
+    """Raised when checkout session is not found."""
+
+    def __init__(self, session_id: str):
+        super().__init__(
+            resource_type="CheckoutSession",
+            identifier=session_id,
+            message=f"Checkout session '{session_id}' not found",
+            error_code="CHECKOUT_SESSION_NOT_FOUND",
+        )
+
+
+class CheckoutSessionExpiredException(BusinessLogicException):
+    """Raised when checkout session has expired."""
+
+    def __init__(self, session_id: str):
+        super().__init__(
+            message="Checkout session has expired",
+            error_code="CHECKOUT_SESSION_EXPIRED",
+            details={"session_id": session_id},
+        )
+
+
+class EmptyCheckoutException(ValidationException):
+    """Raised when trying to checkout with empty cart."""
+
+    def __init__(self):
+        super().__init__(
+            message="Cannot checkout with an empty cart",
+            details={},
+        )
+        self.error_code = "EMPTY_CHECKOUT"
+
+
+class PaymentRequiredException(BusinessLogicException):
+    """Raised when payment is required but not provided."""
+
+    def __init__(self, order_total: float):
+        super().__init__(
+            message="Payment is required to complete this order",
+            error_code="PAYMENT_REQUIRED",
+            details={"order_total": order_total},
+        )
+
+
+class PaymentFailedException(BusinessLogicException):
+    """Raised when payment processing fails."""
+
+    def __init__(self, reason: str, details: dict | None = None):
+        super().__init__(
+            message=f"Payment failed: {reason}",
+            error_code="PAYMENT_FAILED",
+            details={"reason": reason, **(details or {})},
+        )
+
+
+class InvalidShippingAddressException(ValidationException):
+    """Raised when shipping address is invalid or missing."""
+
+    def __init__(self, message: str = "Invalid shipping address", details: dict | None = None):
+        super().__init__(
+            message=message,
+            field="shipping_address",
+            details=details,
+        )
+        self.error_code = "INVALID_SHIPPING_ADDRESS"
+
+
+class ShippingMethodNotAvailableException(BusinessLogicException):
+    """Raised when selected shipping method is not available."""
+
+    def __init__(self, shipping_method: str, reason: str | None = None):
+        message = f"Shipping method '{shipping_method}' is not available"
+        if reason:
+            message += f": {reason}"
+        super().__init__(
+            message=message,
+            error_code="SHIPPING_METHOD_NOT_AVAILABLE",
+            details={"shipping_method": shipping_method, "reason": reason},
+        )
+
+
+class CheckoutInventoryException(BusinessLogicException):
+    """Raised when inventory check fails during checkout."""
+
+    def __init__(self, product_id: int, available: int, requested: int):
+        super().__init__(
+            message=f"Insufficient inventory for product {product_id}",
+            error_code="CHECKOUT_INVENTORY_ERROR",
+            details={
+                "product_id": product_id,
+                "available_quantity": available,
+                "requested_quantity": requested,
+            },
+        )
+
+
+__all__ = [
+    "CheckoutInventoryException",
+    "CheckoutSessionExpiredException",
+    "CheckoutSessionNotFoundException",
+    "CheckoutValidationException",
+    "EmptyCheckoutException",
+    "InvalidShippingAddressException",
+    "PaymentFailedException",
+    "PaymentRequiredException",
+    "ShippingMethodNotAvailableException",
+]