bug: addon items not saving when added to addon groups

[khaira777]

🐛 Bug Report

Description

When creating or editing an addon group on the Products page, addon items (individual addons with name/price) do not persist after saving. The addon group itself saves successfully, but the addons within it are lost.

This means products linked to these addon groups show empty addon groups in the POS AddonModal — the group name and "x remaining" header render, but no selectable addon items appear.

Reproduction Steps

1. Go to Products page → Addon Groups tab
2. Create a new addon group (or edit existing)
3. Click "+ Add Addon" to add addon items with name and price
4. Click Create/Update
5. Reopen the addon group — addon items are gone

Expected Behavior

• Addon items should persist after saving the addon group
• Products linked to the group should show selectable addon items in POS

Actual Behavior

• Addon group saves successfully
• Addon items within the group do not save
• POS AddonModal shows empty addon groups (group header + remaining count, but no addon buttons)

Impact

• 🔴 High — Cannot use addon functionality at all
• Addon groups are useless without selectable items
• Products with addon groups show broken UI in POS

Notes

• Backend code for POST/PUT addon-groups endpoints appears correct (inserts addons in transaction)
• Frontend form correctly sends array in payload
• Need to verify: is the data actually reaching the backend? Check Network tab for request payload and response
• Possibly a silent error being caught by generic error handler

Suggested Investigation

1. Verify the POST/PUT request payload includes the array
2. Check if backend returns the addons in the response
3. Check browser console for any runtime errors
4. Verify database has addon records after save