- SQL migrations 053 (scraper_settings table) + 054 (seed global + per-source rows)
- scraper_settings.py: get_scraper_delay() returns max(per_source, global);
in-memory cache TTL=60s; invalidate_cache() for immediate effect on PUT
- avito/cian/n1 scrapers load delay from DB in __init__ (mirrors yandex pattern)
- Admin API: GET /scraper-settings (list all), PUT /scraper-settings/{source}
with cache invalidation on update; CAST(:d AS numeric) per psycopg v3 rules
- 10 unit tests: global>per_source, per_source>global, global=0, DB error fallback,
cache invalidation, API endpoint smoke
