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/core/config.py

@@ -13,7 +13,6 @@ Note: Environment detection is handled by app.core.environment module.
 This module focuses purely on configuration storage and validation.
 """
 
-from typing import List, Optional
 
 from pydantic_settings import BaseSettings
 
@@ -82,7 +81,7 @@ class Settings(BaseSettings):
     # =============================================================================
     # MIDDLEWARE & SECURITY
     # =============================================================================
-    allowed_hosts: List[str] = ["*"]  # Configure for production
+    allowed_hosts: list[str] = ["*"]  # Configure for production
 
     # Rate Limiting
     rate_limit_enabled: bool = True
@@ -93,7 +92,7 @@ class Settings(BaseSettings):
     # LOGGING
     # =============================================================================
     log_level: str = "INFO"
-    log_file: Optional[str] = None
+    log_file: str | None = None
 
     # =============================================================================
     # PLATFORM DOMAIN CONFIGURATION
@@ -138,9 +137,13 @@ settings = Settings()
 # ENVIRONMENT UTILITIES - Module-level functions
 # =============================================================================
 # Import environment detection utilities
-from app.core.environment import (get_environment, is_development,
-                                  is_production, is_staging,
-                                  should_use_secure_cookies)
+from app.core.environment import (
+    get_environment,
+    is_development,
+    is_production,
+    is_staging,
+    should_use_secure_cookies,
+)
 
 
 def get_current_environment() -> str:
@@ -188,7 +191,7 @@ def is_staging_environment() -> bool:
 # =============================================================================
 
 
-def validate_production_settings() -> List[str]:
+def validate_production_settings() -> list[str]:
     """
     Validate settings for production environment.