feat(transaction-pay-controller): live token balances

[matthewwalsh0]

Explanation

Use live on-chain balance checks to improve stability:

• Before each quote update, refresh the payment token balance via balanceOf or eth_getBalance.
• Before submitting relay deposit transactions, validate the source balance is sufficient.

References

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
Adds new live RPC calls and pre-submit balance gating that can change quote/submit behavior and may surface new failure modes under RPC latency/outages; core transaction submission paths are affected but are covered by updated tests and safe fallback in quoting.

Overview
Adds live on-chain balance checks to pay flows. updateQuotes now refreshes the selected payment token’s balance via a new getLiveTokenBalance RPC read before building quote requests, and uses that live balance when sending sourceBalanceRaw to strategies (falling back to the existing cached balance if the live fetch fails).

Prevents Relay deposits with insufficient funds. Relay submission now validates the current on-chain source token balance against the quote’s required sourceAmount.raw and throws before submitting single or batched transactions when the balance is too low.

Internally this introduces shared amount formatting via computeTokenAmounts, adds @ethersproject/providers to support the new RPC reads, adjusts payment-token change detection to compare address/chainId (case-insensitive), and updates tests/changelog accordingly.

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