Refactor: Update Inventory and process_order to use numerical IDs

[seer-by-sentry]

Fixes ANDROID-19. The issue was that: Flask inventory for item ID 3 insufficient, causing "Not enough inventory" exception, leading to 500 error, triggering Android exception.

• Updated the Inventory dictionary to use numerical IDs instead of string keys.
• Modified the process_order function to handle numerical IDs when checking inventory and updating stock.
• Added more example products to the inventory.

This fix was generated by Seer in Sentry, triggered by [email protected]. 👁️ Run ID: 60738