[Blocker] fix: Transform payload format for VPS backend compatibility

## GitHub Update **Repository:** [MKWcorp/CINTAI](https://github.com/MKWcorp/CINTAI) **Author:** MKWcorp **Date:** 11/9/2025, 7:54:10 AM **Commit:** [`1aa643d`](https://github.com/MKWcorp/CINTAI/commit/1aa643dcb7d5e33abe068154e406438002137ded) ### Commit Message fix: Transform payload format for VPS backend compatibility Problem: VPS backend expects different payload format - userId (not user.id) - userName (not user.name) - message.content (not message string) - history array Solution: Add format transformation in API route - Convert frontend format to backend format - Add fallback values for web users - Add logging for debugging - Better error message in Indonesian This fixes the 'str object has no attribute get' error --- _This story was imported from historical commits._