feat(ui): split external Send into address, From, and amount steps

[romchornyi]

Issue being fixed or feature implemented

The redesigned external Send form (introduced in #819) showed the numeric keypad and amount entry on the address step, and again a second time on the classic amount screen for a plain Core → Core send. The address, source, and amount were not cleanly separated.

What was done?

Split the flow into three screens — address → From → amount:

1. Address (SendScreen) — address field + destination-type badge + invalid-address / source-mismatch validation, clipboard suggestion, and Scan QR. Continue is gated by the new SendViewModel.canAdvanceToAmount. No keypad, no amount.
2. From (SendSourceScreen) — source picker only (Transparent / Platform / Shielded), with a read-only address summary and the chain-sync gate note. No amount.
3. Amount — chosen by the resolved route:
   • Core → Core skips a custom amount screen and continues into the existing classic L1 amount screen (real fee math + its own confirm) via performPay — no double amount entry.
   • Every other leg the L1 screen can't fund — the Core → Shielded asset-lock shield and all Platform/Shielded sources — uses the custom ExternalSendAmountScreen + SendConfirmSheet.

Validations preserved: the chain-sync gate (isBlockedBySync / SyncGateNote) blocks Continue on the From step for Core-funded legs; balance/affordability checks (canContinue) stay on the amount step. Routing under the hood is unchanged. Both hosts push the steps through shared pushExternalSendSource / pushExternalSendAmount extensions, mirroring pushInternalTransfer; the three screens share one SendViewModel.

How Has This Been Tested?

Clean dashpay build (xcodebuild ... -scheme dashpay -sdk iphonesimulator ARCHS=arm64 build). Not yet smoke-tested on testnet across every route — needs a manual pass: Core→Core into the classic amount screen; Core→Shielded / Platform / Shielded into the custom amount screen + confirm; and the balance-row send sheet's Send tab.

Breaking Changes

None.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f92f9986-470f-4386-af07-539305d35d37

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/send-split-address-amount-steps

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}