style: apply black and isort formatting across entire codebase

- Standardize quote style (single to double quotes)
- Reorder and group imports alphabetically
- Fix line breaks and indentation for consistency
- Apply PEP 8 formatting standards

Also updated Makefile to exclude both venv and .venv from code quality checks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/exceptions/inventory.py

@@ -4,7 +4,9 @@ Inventory management specific exceptions.
 """
 
 from typing import Any, Dict, Optional
-from .base import ResourceNotFoundException, ValidationException, BusinessLogicException
+
+from .base import (BusinessLogicException, ResourceNotFoundException,
+                   ValidationException)
 
 
 class InventoryNotFoundException(ResourceNotFoundException):
@@ -14,7 +16,9 @@ class InventoryNotFoundException(ResourceNotFoundException):
         if identifier_type.lower() == "gtin":
             message = f"No inventory found for GTIN '{identifier}'"
         else:
-            message = f"Inventory record with {identifier_type} '{identifier}' not found"
+            message = (
+                f"Inventory record with {identifier_type} '{identifier}' not found"
+            )
 
         super().__init__(
             resource_type="Inventory",
@@ -28,11 +32,11 @@ class InsufficientInventoryException(BusinessLogicException):
     """Raised when trying to remove more inventory than available."""
 
     def __init__(
-            self,
-            gtin: str,
-            location: str,
-            requested: int,
-            available: int,
+        self,
+        gtin: str,
+        location: str,
+        requested: int,
+        available: int,
     ):
         message = f"Insufficient inventory for GTIN '{gtin}' at '{location}'. Requested: {requested}, Available: {available}"
 
@@ -52,10 +56,10 @@ class InvalidInventoryOperationException(ValidationException):
     """Raised when inventory operation is invalid."""
 
     def __init__(
-            self,
-            message: str,
-            operation: Optional[str] = None,
-            details: Optional[Dict[str, Any]] = None,
+        self,
+        message: str,
+        operation: Optional[str] = None,
+        details: Optional[Dict[str, Any]] = None,
     ):
         if not details:
             details = {}
@@ -74,10 +78,10 @@ class InventoryValidationException(ValidationException):
     """Raised when inventory data validation fails."""
 
     def __init__(
-            self,
-            message: str = "Inventory validation failed",
-            field: Optional[str] = None,
-            validation_errors: Optional[Dict[str, str]] = None,
+        self,
+        message: str = "Inventory validation failed",
+        field: Optional[str] = None,
+        validation_errors: Optional[Dict[str, str]] = None,
     ):
         details = {}
         if validation_errors: