feat(scraper): map customer add_time from raw_json

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

yunke-server/app/scraper/whatsapp.py

@@ -248,6 +248,13 @@ def _normalize_whatsapp_friend(record: dict[str, Any]) -> dict[str, Any]:
     and the per-contact counts ``groupNum`` / ``contactsNum`` / ``talkerCount``
     / ``friendAddNum`` / ``sensitiveWordNum`` survive end-to-end even though
     they have no direct ``Customer`` column). ``None``-safe on every field.
+
+    ``add_time`` is deliberately ``None``: the WhatsApp ``businessFriendList``
+    payload carries no customer-side add-time field (the ``createTime`` field
+    on this record is the **owner-staff** account's createTime, not the
+    contact's — confirmed via smoke.db raw_json dump). Mapping it to
+    ``createTime`` would be semantically wrong; the column stays NULL for WA
+    contacts (the wechat channel carries the truthful ``addTime``).
     """
     return {
         "friend_id": record.get("friendUid"),
@@ -259,6 +266,8 @@ def _normalize_whatsapp_friend(record: dict[str, Any]) -> dict[str, Any]:
         "user_id": record.get("userId"),
         "message_count": record.get("messageCount"),
         "last_chat_time": parse_datetime_to_ms(record.get("lastUpdate"), _WA_DATETIME_FORMATS),
+        # No customer-side add-time on this payload (see docstring); left NULL.
+        "add_time": None,
         "version": record.get("version"),
         "raw_json": record,
     }