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>

models/database/product.py

@@ -1,6 +1,8 @@
 # models/database/product.py
 from datetime import datetime
-from sqlalchemy import Boolean, Column, Float, ForeignKey, Index, Integer, String, UniqueConstraint
+
+from sqlalchemy import (Boolean, Column, Float, ForeignKey, Index, Integer,
+                        String, UniqueConstraint)
 from sqlalchemy.orm import relationship
 
 from app.core.database import Base
@@ -12,7 +14,9 @@ class Product(Base, TimestampMixin):
 
     id = Column(Integer, primary_key=True, index=True)
     vendor_id = Column(Integer, ForeignKey("vendors.id"), nullable=False)
-    marketplace_product_id = Column(Integer, ForeignKey("marketplace_products.id"), nullable=False)
+    marketplace_product_id = Column(
+        Integer, ForeignKey("marketplace_products.id"), nullable=False
+    )
 
     # Vendor-specific overrides
     product_id = Column(String)  # Vendor's internal SKU
@@ -34,7 +38,9 @@ class Product(Base, TimestampMixin):
     # Relationships
     vendor = relationship("Vendor", back_populates="products")
     marketplace_product = relationship("MarketplaceProduct", back_populates="product")
-    inventory_entries = relationship("Inventory", back_populates="product", cascade="all, delete-orphan")
+    inventory_entries = relationship(
+        "Inventory", back_populates="product", cascade="all, delete-orphan"
+    )
 
     # Constraints
     __table_args__ = (