Route each scraper source (avito/cian/yandex/domclick) to its own camoufox
browser+proxy so they no longer wedge each other through a single global egress.
Feature-flagged (FEATURE_BROWSER_POOL_ENABLED, default OFF): with the flag off the
/fetch and /login paths are byte-for-byte the existing single-browser behavior.
When on, /fetch routes by body["source"] to a per-proxy browser via BROWSER_PROXY_MAP
(BROWSER_PROXY_AVITO/CIAN/YANDEX/DOMCLICK with legacy fallbacks), each guarded by its
own lazy-launched lock. /login stays single-browser in Phase 1.
BrowserFetcher gains a source arg (default avito) and sends it in the /fetch body;
all scraper callsites pass their source. No docker-compose/.env.runtime changes
(Phase 2, owner-gated).
Replace the system-curl SOCKS5 subprocess transport with the shared
BrowserFetcher (camoufox). camoufox's real-browser fingerprint is not
tarpitted by yandex and does not burn the mobile-proxy IP; raw system-curl
got the proxy IP flagged.
One BrowserFetcher is opened per scraper session in __aenter__ and reused
across all page fetches. _http_get now fetches via the browser, extracts the
gate-API JSON from camoufox's HTML <pre> wrapper, and returns it as the body
of a _CurlResponse (status 200 on success, 0 on fetch/extraction failure) so
all existing callers and the tarpit retry/rotate logic keep working unchanged.
URL building, _parse_gate_json, pagination, combos and field mapping are
untouched. Removed the dead curl subprocess constants/method.
PR #923 switched Cian scrapers to settings.cian_proxy_url but the shared
_mock_settings helper in test_scraper_proxy.py still only exposed scraper_proxy_url,
so pre-existing cian proxy-wiring tests broke with AttributeError → deploy pytest gate failed.
Mirror scraper_proxy_url into cian_proxy_url in the mock.
