fix: GPS only from real check-ins — never from Cantaloupe import

GPS coordinates from Cantaloupe are address-geocoded estimates, not real
field data. Both UPDATE and INSERT paths now set latitude/longitude to
None — GPS comes exclusively from tech check-ins via the main app.

cantaloupe_sync.py

@@ -869,8 +869,8 @@ def approve_batch(
                     if val is not None and str(val).strip() != "":
                         updates[db_col] = str(val).strip()
 
-                # Handle numeric fields
-                for num_field in ("latitude", "longitude", "geofence_radius_meters"):
+                # Handle numeric fields (exclude GPS — comes only from real check-ins)
+                for num_field in ("geofence_radius_meters",):
                     val = item.get(num_field)
                     if val is not None and str(val).strip() != "":
                         try:
@@ -948,8 +948,8 @@ def approve_batch(
                         cust_id,
                         loc_id,
                         1 if cust_name and cust_name.startswith("D-") else 0,
-                        _safe_float(item.get("latitude")),
-                        _safe_float(item.get("longitude")),
+                        None,              # GPS only from real check-ins
+                        None,              # GPS only from real check-ins
                         _safe_int(item.get("geofence_radius_meters"), 50),
                         str(item.get("dex_report_date", "")).strip() or "",
                         str(item.get("deployed", "")).strip() or "",