fix: use fast fee for hw transfer

[piotr-iohk]

Fixes #1088

This PR makes Trezor → spending funding use a faster on-chain fee rate so LSP channel funding confirms more reliably.

Description

• Uses the fast fee tier for hardware-wallet transfer funding instead of the settings default (medium), which can resolve to 1 sat/vB in a quiet fee market.
• Raises the estimate-unavailable fallback from 1 to 3 sat/vB so compose still picks a usable rate when Blocktank fee estimates fail.
• Updates unit coverage for the fast-rate path and the new fallback floor.

Related iOS: synonymdev/bitkit-ios#633

Preview

N/A

QA Notes

Manual Tests

• 1. Pair Trezor with spendable UTXOs → Transfer → Spending → Sign: funding tx uses a fast-tier sat/vB (check explorer), not ~1 sat/vB when the market’s mid is 1.
• 2. Complete HW transfer → Spending: funding confirms and the transfer progresses toward channel open without lingering unconfirmed for hours under a normal fee market.
• 3. regression: Savings → Transfer → Spending: still works with the existing savings fee path.

Automated Checks

• Unit tests modified: assert HW compose requests TransactionSpeed.Fast and uses a 3 sat/vB fallback when fee lookup fails in TransferViewModelTest.kt.
• Local: just test file TransferViewModelTest, just lint.
• CI: standard compile, unit test, and detekt checks run by the PR bot.

Made with Cursor

[greptile-apps]

Greptile Summary

This PR uses faster fees for hardware-wallet funding. The main changes are:

• Requests the fast fee tier for Trezor-to-spending transfers.
• Raises the unavailable-estimate fallback from 1 to 3 sat/vB.
• Updates unit coverage and the changelog.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
app/src/main/java/to/bitkit/viewmodels/TransferViewModel.kt	Uses the fast fee tier for hardware-wallet funding and raises the fallback fee rate to 3 sat/vB.
app/src/test/java/to/bitkit/viewmodels/TransferViewModelTest.kt	Verifies the fast fee request and updates the expected fallback fee rate.
changelog.d/next/1088.fixed.md	Documents the improved confirmation reliability for hardware-wallet transfers.

_{Reviews (1): Last reviewed commit: "chore: rename changelog fragment" | Re-trigger Greptile}

[piotr-iohk]

Tested end-to-end on mainnet (Trezor → spending / Blocktank channel open).

• Funding tx used ~3 sat/vB (not the previous ~1 sat/vB mid/default path).
• Tx confirmed within minutes and the channel opened successfully.
• Previously the same flow could sit unconfirmed for hours at ~1 sat/vB.

Fix confirmed end-to-end on mainnet.

[pwltr]

Failing e2e test seems valid on first glance, also note related issue #1034

[piotr-iohk]

Will address savings → spending (onTransferToSpendingConfirm / #1034) separately — that path needs more than a fee-tier swap (fee headroom / send-all edge cases under fast rates). This PR stays a targeted HW-wallet funding fee fix for #1088.

[jvsena42]

I'll handle #1034