fix(transaction-pay-controller): proxy Across status polling via configured api base

[pedronfigueiredo]

Summary

• route Across status polling through the configured Across apiBase instead of the direct upstream URL
• poll Across deposit status with depositTxnRef and accept fillTxnRef as a terminal transaction hash fallback
• read confirmations_pay from remote feature flags or local overrides, and use http://localhost:3000/across when confirmations_pay.dev is enabled without an explicit Across base
• add focused tests and changelog coverage for the new behavior

Validation

• yarn workspace @metamask/transaction-pay-controller run jest --no-coverage src/strategy/across/across-submit.test.ts src/utils/feature-flags.test.ts
• yarn eslint packages/transaction-pay-controller/src/strategy/across/across-submit.ts packages/transaction-pay-controller/src/strategy/across/across-submit.test.ts packages/transaction-pay-controller/src/utils/feature-flags.ts packages/transaction-pay-controller/src/utils/feature-flags.test.ts
• yarn workspace @metamask/transaction-pay-controller run changelog:validate
• yarn build

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Note

Medium Risk
Touches Across bridging completion logic and status polling parameters/base URL; misconfiguration or unexpected API response shapes could cause submissions to appear stuck or resolve to the wrong final hash.

Overview
Across submission now polls the /deposit/status endpoint via the configured confirmations_pay.payStrategies.across.apiBase (instead of relying on quote-provided/upstream URL details) and uses the source transaction hash as depositTxnRef.

Status completion handling is updated to accept fillTxnRef as an additional terminal transaction hash fallback (before fillTxHash/txHash). Tests are adjusted/added to assert the new polling URL/params and hash fallback behavior, and the changelog documents the fix.

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