feat(rank-tracking): opt-in env toggles to run manual rank checks via the task queue

[redrammedia]

Motivation

Scheduled rank checks already use DataForSEO's standard task queue (~30% of the live endpoint's cost), but manual "Check now" runs always pay live prices. For self-hosters who track a few hundred keywords and don't mind waiting a few minutes, that's a ~3.3x cost difference with identical data — both paths send the same request parameters and parse results through the same buildRankCheckResult.

This PR adds two opt-in env toggles so self-hosters can choose cost over speed. Default behavior is completely unchanged — without the variables set, every code path resolves to today's behavior.

Changes

RANK_CHECK_MANUAL_METHOD=queued routes manual checks through the existing runQueuedCheck path (task_post → task_get polling → live fallback). The decision is resolved inside the durable "prepare" workflow step via a new resolveRankCheckMethod() helper, so it survives workflow replays. The credit pre-check estimates at queued pricing accordingly.

RANK_CHECK_QUEUE_LIVE_FALLBACK=off disables the live fallback for queued stragglers (some self-hosters prefer "never bill live prices" over completeness). To compensate, the polling window extends from ~15 minutes to ~2¼ hours (cumulative waits 4/6/8/10/12/15/30/45/60/75/105/135 min). Anything still missing afterwards is reported by the existing finalize logic as "could not be checked" instead of being re-billed live.

Cost estimate follows the resolved method: RankTrackingService.estimateCost and the check-confirm dialog show queued pricing and realistic timing ("~5-15 min (task queue)") when the toggle is active, live pricing otherwise. Saving config edits now also invalidates the cached cost estimate so the header price updates without a reload (a small pre-existing staleness bug that also affects the default setup).

compose.yaml forwards both variables into the self-host container; docs/SELF_HOSTING_CLOUDFLARE.md documents them.

Testing

• New unit tests for resolveRankCheckMethod / resolveQueueLiveFallback (7 cases).
• pnpm ci:check, pnpm test:ci, pnpm vite build all pass.
• Verified end-to-end on a self-hosted Docker install: with the toggles set, a manual 140-keyword check ran fully through the queue (140 posted, 140 collected, 0 live fallbacks, ~6 min) at queued cost; without the variables, behavior is byte-identical to main.

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