run_avito_full_load gains incremental_days param -> passes since= to the
(merged) incremental SERP engine. avito_full_load schedule flipped to
incremental_days=2 (shallow, date early-stop -> avoids deep-pagination 429
bans). New avito_full_load_exhaustive source runs the full walk weekly to
refresh last_seen (10-day delisting TTL) and catch silent price edits.
