🤖 Fix insufficient inventory exception in checkout process

[sentry-autofix]

👋 Hi there! This PR was automatically generated 🤖

Fixes FLASK-146

The checkout functionality throws an exception indicating "Not enough inventory for product" due to an incorrect comparison logic in the inventory check. The logic should verify that each cart item quantity does not exceed the available inventory for that item before proceeding with the checkout.

The steps that were performed:

1. Correct inventory check logic
2. Enhance empty inventory or cart logic

📣 Instructions for the reviewer which is you, yes you:

• If these changes were incorrect, please close this PR and comment explaining why.
• If these changes were incomplete, please continue working on this PR then merge it.
• If you are feeling confident in my changes, please merge this PR.

This will greatly help us improve the autofix system. Thank you! 🙏

If there are any questions, please reach out to the AI/ML Team on #proj-autofix

🤓 Stats for the nerds:

Prompt tokens: 22817
Completion tokens: 1369
Total tokens: 24186