[Grocery List] Add custom grocery list management module

[AhsanIdrees121]

This PR introduces a custom Odoo module for managing grocery lists.

Features

• Create and manage grocery lists
• Assign responsible user
• Add products with quantities
• Mark items as purchased
• Automatic list completion when all items are purchased

Technical Notes

• Follows Odoo ORM and security best practices
• Access control enforced for item updates
• No core files modified

Testing

• Module installed successfully
• CRUD operations tested
• Access rights verified