feat(crawler): captcha solving + per-attempt billing (Phase 3d)

Wire captchatools as the StealthyFetcher-tier page_action to detect, harvest
(egressing from the crawl's own proxy IP), inject, and submit reCAPTCHA v2/v3
and hCaptcha tokens. Opt-in and off by default (zero attempts, zero cost).

Licensing split:
- Apache-2 app/utils/captcha/ holds the generic, vendor-agnostic config
  (CaptchaConfig + captcha_enabled() = flag AND key present).
- Proprietary app/proprietary/web_crawler/captcha.py holds the bypass logic
  (detect/harvest/inject) plus a process-wide solver latch that halts solving
  on unrecoverable errors (no balance / bad key).

Crawler: CrawlOutcome gains captcha_attempts/captcha_solved, surfaced via a
per-call captcha_state dict threaded crawl_url -> _crawl_with_stealthy(_sync)
and stamped onto every stealth terminal outcome. The stealth tier captures the
proxy once and reuses it for both the fetch and the solver (IP-coherence).

Billing: WebCrawlCreditService gains captcha_billing_enabled,
captcha_solves_to_micros, charge_captcha, and a generic check_balance, sharing
a single _apply_debit path. The indexer accumulates attempts (even on failed
crawls), runs a combined crawl+captcha pre-flight, and posts a per-attempt
owner charge as usage_type="web_crawl_captcha". The captcha worst-case is only
reserved when solving is actually enabled, so a solving-off deployment is never
blocked for captcha that can never run. Both chat scrape tools fold attempts
into the current turn before the success/fail branch.

Fully config-driven prices; no migration. New unit tests cover the config,
factory (detection/latch/timeout/cap), credit service, indexer wiring, and the
chat fold.

Co-authored-by: Cursor <cursoragent@cursor.com>

surfsense_backend/app/utils/captcha/__init__.py

@@ -0,0 +1,22 @@
+"""App-wide captcha-solver configuration (Apache-2.0, generic glue).
+
+This package holds only the **generic, vendor-agnostic** config resolution for
+captcha solving — mirroring ``app/utils/proxy/`` (which stays Apache-2.0 even
+though the crawler that consumes it is proprietary). The actual bypass logic
+(challenge detection + token injection ``page_action``) lives in the separately
+licensed ``app/proprietary/web_crawler/captcha.py``.
+
+``captchatools`` is itself the multi-vendor registry (capmonster / 2captcha /
+anticaptcha / capsolver / captchaai), so there is no provider hierarchy here —
+just one env-driven :class:`CaptchaConfig` and a cheap ``captcha_enabled()``
+gate callers check before constructing anything (mirrors
+``WebCrawlCreditService.billing_enabled()``).
+"""
+
+from app.utils.captcha.config import (
+    CaptchaConfig,
+    captcha_enabled,
+    get_captcha_config,
+)
+
+__all__ = ["CaptchaConfig", "captcha_enabled", "get_captcha_config"]