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>

models/database/vendor.py

@@ -5,13 +5,23 @@ Vendor model representing entities that sell products or services.
 This module defines the Vendor model along with its relationships to
 other models such as User (owner), Product, Customer, Order, and MarketplaceImportJob.
 """
+
 import enum
 
-from sqlalchemy import (JSON, Boolean, Column, DateTime, ForeignKey, Integer,
-                        String, Text)
+from sqlalchemy import (
+    JSON,
+    Boolean,
+    Column,
+    DateTime,
+    ForeignKey,
+    Integer,
+    String,
+    Text,
+)
 from sqlalchemy.orm import relationship
 
 from app.core.config import settings
+
 # Import Base from the central database module instead of creating a new one
 from app.core.database import Base
 from models.database.base import TimestampMixin