fix: route fiat payment method through strategy selection to enable fiat strategy

[OGPoyraz]

Explanation

The fiat strategy was never selected during quote retrieval because of two issues:

1. getStrategyOrder never included Fiat — The default strategy order only contained Relay and Across. The fiat payment method ID was not passed into the strategy routing function, so TransactionPayStrategy.Fiat was never part of the strategy list.

2. getQuotes bailed early on empty requests — When a fiat payment method is selected without a crypto payment token, buildQuoteRequests returns an empty array (no paymentToken). The guard if (!requests?.length) short-circuited before any strategy could run. The fiat strategy doesn't need these requests — it derives its own relay request from amountFiat internally.

Changes

• getStrategyOrder — Added optional fiatPaymentMethodId parameter. When provided, early returns [TransactionPayStrategy.Fiat] so only the fiat strategy is used.
• #getStrategiesWithFallback — Now passes transactionData.fiatPayment.selectedPaymentMethodId through to getStrategyOrder.
• getQuotes — Changed the empty-requests guard from !requests?.length to !requests?.length && !fiatPaymentMethod so the strategy loop runs when a fiat payment method is active.

References

• Related to CONF-1065

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Changes strategy routing and quote retrieval guard logic, which can affect which pay strategy executes and when quotes are fetched, but scope is limited to the transaction-pay controller and covered by new unit tests.

Overview
Fixes fiat pay quote retrieval by threading fiatPayment.selectedPaymentMethodId into strategy selection and ensuring it can drive the Fiat strategy.

getStrategyOrder now accepts an optional fiat payment method ID and short-circuits to Fiat-only strategy ordering when present, and TransactionPayController passes this value through during fallback strategy resolution. Quote retrieval no longer bails early on empty request sets when a fiat payment method is selected, allowing fiat quotes even without a crypto paymentToken.

Adds targeted test coverage for the new routing behavior and updates the package changelog under Fixed.

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