fix(tradein): cian _rotate_ip uses cian_proxy_rotate_url; page-scope idiom

Review #926 fixups:
- _rotate_ip: cian_proxy_rotate_url or avito_proxy_rotate_url (was avito-only →
  rotated wrong proxy IP on Cian ban, ignored CIAN_PROXY_ROTATE_URL).
- pagination log: dir() → locals() for local-var existence check.

tradein-mvp/backend/app/services/scrapers/cian.py

@@ -155,7 +155,7 @@ class CianScraper(BaseScraper):
         мобильному модему нужно время поднять новый IP. Returns True при успехе.
         Зеркало AvitoScraper._rotate_ip (#623).
         """
-        rotate_url = settings.avito_proxy_rotate_url
+        rotate_url = settings.cian_proxy_rotate_url or settings.avito_proxy_rotate_url
         if not rotate_url:
             return False
         sep = "&" if "?" in rotate_url else "?"
@@ -573,7 +573,7 @@ class CianScraper(BaseScraper):
             room_label,
             lo,
             hi,
-            min(max_pages, page if "page" in dir() else 1),
+            min(max_pages, page if "page" in locals() else 1),
             max_pages,
             collected_this_bucket,
             len(seen),