fix(backend): sanitize NaN/Infinity/undefined in Gemini JSON response

Models sometimes emit JS-style literals for unknown numeric fields.
Replace NaN, Infinity, undefined with null before parsing.
Also add error logging to capture raw response on parse failure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/innercontext/api/products.py

@@ -1,8 +1,12 @@
 import json
+import logging
+import re
 from datetime import date
 from typing import Optional
 from uuid import UUID, uuid4
 
+log = logging.getLogger(__name__)
+
 from fastapi import APIRouter, Depends, HTTPException, Query
 from google.genai import types as genai_types
 from pydantic import ValidationError
@@ -369,9 +373,14 @@ def parse_product_text(data: ProductParseRequest) -> ProductParseResponse:
         end = raw.rfind("}")
         if start != -1 and end != -1:
             raw = raw[start : end + 1]
+    # Replace JS-style non-JSON literals that some models emit
+    raw = re.sub(r":\s*NaN\b", ": null", raw)
+    raw = re.sub(r":\s*Infinity\b", ": null", raw)
+    raw = re.sub(r":\s*undefined\b", ": null", raw)
     try:
         parsed = json.loads(raw)
-    except (json.JSONDecodeError, Exception) as e:
+    except json.JSONDecodeError as e:
+        log.error("Gemini parse-text raw response (failed):\n%s", raw)
         raise HTTPException(status_code=502, detail=f"LLM returned invalid JSON: {e}")
     try:
         return ProductParseResponse.model_validate(parsed)