refactor: modernize code quality tooling with Ruff

- Replace black, isort, and flake8 with Ruff (all-in-one linter and formatter)
- Add comprehensive pyproject.toml configuration
- Simplify Makefile code quality targets
- Configure exclusions for venv/.venv in pyproject.toml
- Auto-fix 1,359 linting issues across codebase

Benefits:
- Much faster builds (Ruff is written in Rust)
- Single tool replaces multiple tools
- More comprehensive rule set (UP, B, C4, SIM, PIE, RET, Q)
- All configuration centralized in pyproject.toml
- Better import sorting and formatting consistency

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

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

app/exceptions/customer.py

@@ -3,11 +3,15 @@
 Customer management specific exceptions.
 """
 
-from typing import Any, Dict, Optional
+from typing import Any
 
-from .base import (AuthenticationException, BusinessLogicException,
-                   ConflictException, ResourceNotFoundException,
-                   ValidationException)
+from .base import (
+    AuthenticationException,
+    BusinessLogicException,
+    ConflictException,
+    ResourceNotFoundException,
+    ValidationException,
+)
 
 
 class CustomerNotFoundException(ResourceNotFoundException):
@@ -71,8 +75,8 @@ class CustomerValidationException(ValidationException):
     def __init__(
         self,
         message: str = "Customer validation failed",
-        field: Optional[str] = None,
-        details: Optional[Dict[str, Any]] = None,
+        field: str | None = None,
+        details: dict[str, Any] | None = None,
     ):
         super().__init__(message=message, field=field, details=details)
         self.error_code = "CUSTOMER_VALIDATION_FAILED"