fix(explorer): address browser-audited funding regressions

Parent tracker: #436
Owning PR: #431
Depends on: #444 / PR #430

## Goal

Repair the browser-audited money, chain, and card-recovery regressions on top of the funding stack.

## Scope

- Block impossible direct-deposit amounts before submission.
- Poll each transaction receipt on the chain where that transaction was submitted.
- Keep rail settlement tied to the displayed Filecoin chain and account while temporary source-chain switches occur.
- Persist card recovery only after Privy authoritatively reports submission or confirmation.
- Ignore and self-heal legacy ambiguous recovery markers.

## Non-goals

- Performing a live payment.
- Restacking, merging, or resolving the current PR conflict.
- Broadening the funding UX beyond the audited regressions.

## Acceptance criteria

- An amount above the available balance cannot be submitted.
- Receipt polling never follows the wallet onto the wrong chain.
- Rail settlement does not follow a temporary Base-network switch.
- Cancellation before provider submission leaves no durable recovery marker.
- Only an explicit submitted or confirmed provider result creates recoverable state.
- Focused tests cover each invariant and legacy ambiguous markers.

## Performance

Performance is not the objective. The correctness and recovery paths must remain bounded, with no new unbounded polling or storage growth.

## Delivery

PR #431 remains based on PR #430 while the stack is open. After its predecessor merges, retarget it to staging and revalidate the exact head. Its current conflict is tracked as a separate readiness concern, not changed by this metadata cleanup.

Start with owning PR #431, its base PR #430, and dependency #444 to understand the funding-stack changes and current conflict. Review the focused tests for each listed invariant; done means the acceptance criteria pass, including bounded polling and correct handling of legacy recovery markers, without broadening the funding UX.

Written by the indexing model from the issue text.