refactor(tradein/scraper-kit): domclick providers on shared _base.py (#2364)

Group F4d (epic #2277, parent #2352). Migrated the ad-hoc BrowserFetcher
construction in providers/domclick/serp.py::fetch_city to the shared
build_browser_fetcher(config, source) helper from Foundation (#2358).

Scope actually touched:
- serp.py: replaced the local BrowserFetcher(source="domclick", endpoint=...)
  construction with build_browser_fetcher(self._config, "domclick").
- detail.py: NO changes needed. Grepped for BrowserFetcher(/AsyncSession(/
  curl_cffi and found none - fetch_detail() receives an already-constructed
  browser_fetcher from the caller (orchestrator owns the session lifecycle,
  per its own module docstring), so there was nothing to migrate here.

Caveat verified (same class as avito, per issue instructions): the old
call site omitted use_pool, so it implicitly defaulted to False via the
BrowserFetcher class default. build_browser_fetcher(config, source) reads
use_pool=config.use_proxy_pool_browser instead - a real difference in the
value passed in. However this call site does not pass proxy_provider
(stays the default None), and BrowserFetcher._pool_proxy computes
`use_pool and proxy_provider is not None` before ever using the pool - so
with proxy_provider=None the effective behavior is identical regardless
of what use_pool evaluates to (confirmed by reading browser_fetcher.py
directly, matching the build_browser_fetcher docstring's own note that
domclick is one of the providers not yet wired to the proxy pool, #2160
P4). No observable behavior change. Documented inline at the call site.

Tests: domclick-specific suite (91 tests: golden parity, sweep, admin
ingest parity, detail + detail kit parity) all green, plus cross-provider
test_scraper_kit_pipeline_parity2.py (8 tests). Full backend suite:
3278 passed, 6 skipped, 1 pre-existing flake (test_search_cache_hit,
#2208) - no new failures.

tradein-mvp/packages/scraper-kit/src/scraper_kit/providers/domclick/serp.py

@@ -311,14 +311,20 @@ class DomClickScraper(BaseScraper):
         """
         # TODO Layer B (#1846 follow-up): backfill renovation/wallType/priceHistory
 
-        from scraper_kit.browser_fetcher import BrowserFetcher
+        from scraper_kit.providers._base import build_browser_fetcher
 
         out_lots: list[ScrapedLot] = []
         seen_ids: set[str] = set()
 
-        async with BrowserFetcher(
-            source="domclick", endpoint=self._config.browser_http_endpoint
-        ) as fetcher:
+        # build_browser_fetcher(config, source) без proxy_provider (дефолт None) —
+        # поведенчески идентично прежнему прямому BrowserFetcher(source=..., endpoint=...):
+        # use_pool теперь читает config.use_proxy_pool_browser (#2364 caveat, тот же
+        # класс что и avito) вместо хардкода False, но BrowserFetcher._pool_proxy
+        # вычисляет `use_pool and proxy_provider is not None` — при proxy_provider=None
+        # результат всегда False независимо от значения флага (см. _base.py
+        # build_browser_fetcher docstring: domclick пока не подключён к browser-proxy-
+        # пулу, #2160 P4 wiring gap). Поведение НЕ меняется.
+        async with build_browser_fetcher(self._config, "domclick") as fetcher:
             for bucket in ROOM_BUCKETS:
                 logger.info(
                     "domklik: BFF sweep rooms=%r city_id=%d pages_cap=%d",