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/vendor.py

@@ -4,13 +4,10 @@ Vendor management specific exceptions.
 """
 
 from typing import Any, Dict, Optional
-from .base import (
-    ResourceNotFoundException,
-    ConflictException,
-    ValidationException,
-    AuthorizationException,
-    BusinessLogicException
-)
+
+from .base import (AuthorizationException, BusinessLogicException,
+                   ConflictException, ResourceNotFoundException,
+                   ValidationException)
 
 
 class VendorNotFoundException(ResourceNotFoundException):
@@ -82,10 +79,10 @@ class InvalidVendorDataException(ValidationException):
     """Raised when vendor data is invalid or incomplete."""
 
     def __init__(
-            self,
-            message: str = "Invalid vendor data",
-            field: Optional[str] = None,
-            details: Optional[Dict[str, Any]] = None,
+        self,
+        message: str = "Invalid vendor data",
+        field: Optional[str] = None,
+        details: Optional[Dict[str, Any]] = None,
     ):
         super().__init__(
             message=message,
@@ -99,10 +96,10 @@ class VendorValidationException(ValidationException):
     """Raised when vendor validation fails."""
 
     def __init__(
-            self,
-            message: str = "Vendor validation failed",
-            field: Optional[str] = None,
-            validation_errors: Optional[Dict[str, str]] = None,
+        self,
+        message: str = "Vendor validation failed",
+        field: Optional[str] = None,
+        validation_errors: Optional[Dict[str, str]] = None,
     ):
         details = {}
         if validation_errors:
@@ -120,9 +117,9 @@ class IncompleteVendorDataException(ValidationException):
     """Raised when vendor data is missing required fields."""
 
     def __init__(
-            self,
-            vendor_code: str,
-            missing_fields: list,
+        self,
+        vendor_code: str,
+        missing_fields: list,
     ):
         super().__init__(
             message=f"Vendor '{vendor_code}' is missing required fields: {', '.join(missing_fields)}",