feat(explorer): show Squid rates and execution progress

Parent tracker: #436
Owning PR: #422
Depends on: #437 / PR #421

## Goal

Show the user the quoted Squid rate, minimum received amount, and stable step-by-step execution progress.

## Scope

- Display rate and minimum-received details in review.
- Number transaction progress consistently.
- Keep review and progress state stable across wallet updates.
- Present concise actionable errors.

## Non-goals

- Changing quote selection or fee-budget policy.
- Restacking, merging, or otherwise changing PR state.

## Acceptance criteria

- Review shows the rate and minimum receive amount supplied by the active quote.
- Progress identifies the current transaction and total transaction count.
- Wallet updates do not reset a transaction already in progress.
- Focused tests cover review details, progress, wallet updates, and errors.

## Performance

No material performance impact is expected; this is presentation and state-stability work.

## Delivery

PR #422 remains based on PR #421 while the stack is open. After its predecessor merges, retarget it to staging and revalidate the exact head.

Start with parent tracker #436 and owning PR #422, then inspect dependency #437 and PR #421 to understand the current review, progress, wallet-update, and error work. Done means meeting the acceptance criteria with focused tests covering review details, progress, wallet updates, and errors, then retargeting and revalidating the stacked PR as described.

Written by the indexing model from the issue text.