feat: add boltz savings swap

[coreyphillips]

This PR adds a swap-based path for transferring spending balance to savings, so Lightning funds can move on-chain through a Boltz reverse swap instead of only by closing a channel.

Description

• Adds a Boltz reverse swap flow to the transfer-to-savings journey. The confirm screen now shows a live quote (amount to savings, network fee, service fee, and the amount you will receive) and lets the user proceed with a swap or fall back to closing the channel.
• Guards against amounts that are too low to swap, holding back a small reserve for Lightning routing fees and surfacing a clear message when the amount cannot be transferred.
• Waits for the on-chain claim during the progress step and resumes any pending swaps when the wallet starts, refreshing balances automatically once a swap lands on-chain. The updates stream now also stops with the node when the app goes to background.
• Adds a Swaps section under Dev Settings to list swaps and claim a reverse swap, backed by a new service that wraps the Boltz module. The manual claim button only shows while the swap is actually claimable (lockup on-chain and no claim broadcast yet).
• Adds a reusable slider component used by the swap amount controls.
• Bumps bitkit-core to 0.5.1, which introduces the Boltz module this flow depends on.

Preview

QA Notes

Manual Tests (Must use mainnet for now)

• 1. With a spending balance, Transfer to Savings → Savings Confirm: quote shows amount to savings, network fee, service fee, and you'll receive.
• 2. Savings Confirm → change amount: quote recomputes for the new amount.
• 3. Savings Confirm → set an amount below the swap minimum: amount-too-low message shows and confirm is blocked.
• 4a. Savings Confirm → confirm swap → Savings Progress: completes after the on-chain claim.
  • 4b. After claim: savings balance reflects the swapped funds without a manual sync.
• 5. regression: Savings Confirm → Close channel instead: falls back to the channel-close path.
• 6. regression: Start the app with a pending swap: swap resumes and balance updates once it lands on-chain.
• 7a. Dev Settings → Swaps → tap a swap → Swap Detail: Claim now shows only for an unclaimed reverse swap with its lockup in mempool or confirmed.
  • 7b. Swap Detail of a created, expired, refunded, or claimed swap: no Claim button.

Automated Checks

• Unit tests added: savings swap quote limits, slider clamping, swap execution outcomes (claimed, error, timeout, payment failure), and that a second start is ignored while a swap is in flight, in TransferViewModelTest.kt.
• Unit tests added: claimable status gating, swap list sorting, and manual claim in SwapsViewModelTest.kt.
• Unit tests modified: inject the new Boltz service dependency into the wallet view model setup in WalletViewModelTest.kt.
• Ran locally against bitkit-core 0.5.1: compileDevDebugKotlin, testDevDebugUnitTest, and detekt all pass.

[greptile-apps]

Greptile Summary

This PR adds a Boltz reverse-swap path for moving Lightning funds into on-chain savings. The main changes are:

• Live swap quotes, fee details, and adjustable transfer amounts.
• Background swap execution, claim tracking, and pending-swap recovery.
• A settling state for swaps whose claims have not landed yet.
• Developer screens for listing and manually claiming swaps.
• A reusable amount slider and the required bitkit-core update.

Confidence Score: 5/5

This looks safe to merge.

• The latest changes address the event subscription and screen lifecycle races.
• Swap update startup now retries, and claim events trigger balance refreshes.
• Pending claims are shown as settling instead of completed.
• No blocking issue was found in the updated code.

Important Files Changed

Filename	Overview
app/src/main/java/to/bitkit/viewmodels/TransferViewModel.kt	Owns swap execution beyond the screen lifecycle, prevents concurrent starts, cancels stale quote requests, and subscribes before invoice payment.
app/src/main/java/to/bitkit/viewmodels/WalletViewModel.kt	Starts claim event collection before the update stream, retries stream startup, and stops updates with the wallet lifecycle.
app/src/main/java/to/bitkit/ui/screens/transfer/SavingsProgressScreen.kt	Observes swap outcomes and displays pending claims as settling rather than completed.
app/src/main/java/to/bitkit/ui/screens/transfer/SavingsConfirmScreen.kt	Adds swap quotes, amount controls, fee details, and channel-close fallback behavior.
app/src/main/java/to/bitkit/services/BoltzService.kt	Wraps Boltz swap creation, queries, claims, refunds, and lifecycle event streaming.

_{Reviews (2): Last reviewed commit: "fix: fall back to close when swap amount..." | Re-trigger Greptile}