fix: use blue accent on hw send confirm screen

[jvsena42]

Fixes #1259

This PR makes the Send confirm screen use the blue hardware accent when the funding source is a hardware wallet, instead of the orange on-chain accent.

Description

• Derives the confirm screen's accent color from the funding source as well as the payment method, so a hardware-funded on-chain send shows the blue accent on the swipe slider and the show/hide details icon. Previously the accent came from the payment method alone, so hardware sends looked identical to sends from savings.
• Keeps the confirming-in clock icon on the brand accent, matching the iOS confirm screen, so only the elements that signal the funding source change color.
• Adds a hardware variant preview of the confirm screen, so the blue state is visible in Compose previews next to the existing savings and lightning ones.

The accent now matches iOS, where the same screen already returns the blue accent while a hardware send is active, and matches the funding-source chip on this screen, which has always been blue for hardware.

Design

Reporting an honest conflict rather than a clean match. The hardware variant of this screen is designed in Send (Hardware Device) (On-chain) › Confirm Send Onchain and › Confirm Send Onchain Details on Handoff v62. Both frames show the swipe slider, the speed-and-fee icon and the details icon in the orange on-chain accent, with only the FROM chip in blue — which is what Android shipped and what this PR changes.

The change follows the issue and iOS instead of those frames. Worth a designer call on which one is correct before this merges; if the frames are the intended behaviour, this PR should be closed and the issue reclassified rather than merged.

Related: #1201, #1203, #998.

Preview

QA Notes

Manual Tests

• 1. Paired hardware wallet with spendable sats → Send → paste an address → pick the hardware wallet as funding source → Confirm: swipe slider and Show Details icon are blue.
  • 1b. Show Details: FROM chip is blue, confirming-in clock icon stays orange.
• 2. regression: Confirm → switch funding source back to Savings: slider and details icon return to orange.
• 3. regression: Send a LN invoice → Confirm: slider and details icon stay purple.
• 4. regression: Hardware Confirm → swipe to pay: signing flow starts as before; no behaviour change beyond color.

Automated Checks

• Instrumented tests added in SendConfirmScreenTest.kt: render the confirm screen and count accent pixels in the captured bitmap, asserting blue with a hardware funding source and orange without one. Verified the blue test fails against the pre-fix accent logic and passes after it, on a Pixel 9 emulator.
• just compile, just test, and just lint pass locally.

🤖 Generated with Claude Code

https://claude.ai/code/session_01KavTcT18zALriWtzY57GTR