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/inventory.py

@@ -1,6 +1,8 @@
 # models/database/inventory.py
 from datetime import datetime
-from sqlalchemy import Column, ForeignKey, Index, Integer, String, UniqueConstraint
+
+from sqlalchemy import (Column, ForeignKey, Index, Integer, String,
+                        UniqueConstraint)
 from sqlalchemy.orm import relationship
 
 from app.core.database import Base
@@ -27,7 +29,9 @@ class Inventory(Base, TimestampMixin):
 
     # Constraints
     __table_args__ = (
-        UniqueConstraint("product_id", "location", name="uq_inventory_product_location"),
+        UniqueConstraint(
+            "product_id", "location", name="uq_inventory_product_location"
+        ),
         Index("idx_inventory_vendor_product", "vendor_id", "product_id"),
         Index("idx_inventory_product_location", "product_id", "location"),
     )