PR #1764's reconnect-retry was dead code in prod: the gate excluded configs
with avito_proxy_rotate_url set, but prod has BOTH the backconnect SCRAPER_PROXY_URL
(what curl_cffi egresses through) AND a leftover changeip URL for the separate
auv/browser proxy. With max_rotations=0 neither path fired -> a single SERP 403
still aborted the sweep (run 212). The curl session always uses scraper_proxy_url,
so session-rebuild rotates the exit IP regardless of changeip config.
Under a backconnect rotating proxy (no changeip URL) a single HTTP 403 or
firewall interstitial aborted the entire avito_full_load sweep via
AvitoBlockedError -> mark_banned. Each new connection through backconnect
gets a fresh exit IP, so retry by rebuilding the curl_cffi session up to
_AVITO_403_MAX_RETRIES times before giving up. Legacy single-IP changeip
rotation and browser-mode paths unchanged. Mirrors existing 429 short-retry.
