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

• 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 savings. The main changes are:

• Live swap limits, fee quotes, and adjustable transfer amounts.
• Reverse-swap creation, payment, claim tracking, and startup resumption.
• Swap history, detail, and manual claim tools in developer settings.
• A reusable amount slider and a bitkit-core dependency update.

Confidence Score: 4/5

The swap lifecycle can report completion too early and can lose claim handling during startup, navigation, or event-subscription races.

• Pending swaps are shown as completed transfers.
• Claim events can arrive before collectors subscribe.
• Failed background update startup is not retried.
• Concurrent quote requests can restore stale amounts.

TransferViewModel.kt, SavingsProgressScreen.kt, and WalletViewModel.kt

Important Files Changed

Filename	Overview
app/src/main/java/to/bitkit/viewmodels/TransferViewModel.kt	Adds quote calculation and reverse-swap execution, with races in quote replacement and claim-event subscription.
app/src/main/java/to/bitkit/ui/screens/transfer/SavingsProgressScreen.kt	Adds swap progress handling but treats pending swaps as complete and ties execution to the screen lifecycle.
app/src/main/java/to/bitkit/viewmodels/WalletViewModel.kt	Adds swap resumption and balance refresh handling without retrying failed stream startup.
app/src/main/java/to/bitkit/services/BoltzService.kt	Adds the Boltz FFI wrapper and a non-replaying event bridge used by swap execution and wallet updates.
app/src/main/java/to/bitkit/ui/screens/transfer/SavingsConfirmScreen.kt	Adds live quotes, amount adjustment, swap confirmation, and the channel-close fallback.
app/src/main/java/to/bitkit/viewmodels/SwapsViewModel.kt	Adds sorted swap history, manual claims, and status-based claim gating.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant UI as Savings Progress
    participant TVM as TransferViewModel
    participant LN as LightningRepo
    participant Boltz as BoltzService
    participant WVM as WalletViewModel
    UI->>TVM: executeSavingsSwap()
    TVM->>Boltz: createReverseSwap()
    TVM-->>Boltz: schedule event collection
    TVM->>LN: pay hold invoice
    Boltz-->>TVM: Claimed or Error
    alt Event observed
        TVM-->>UI: Success or Failure
    else No event within 60 seconds
        TVM-->>UI: Pending
        UI-->>UI: Show success
        WVM->>Boltz: Continue background updates
    end

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%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
    participant UI as Savings Progress
    participant TVM as TransferViewModel
    participant LN as LightningRepo
    participant Boltz as BoltzService
    participant WVM as WalletViewModel
    UI->>TVM: executeSavingsSwap()
    TVM->>Boltz: createReverseSwap()
    TVM-->>Boltz: schedule event collection
    TVM->>LN: pay hold invoice
    Boltz-->>TVM: Claimed or Error
    alt Event observed
        TVM-->>UI: Success or Failure
    else No event within 60 seconds
        TVM-->>UI: Pending
        UI-->>UI: Show success
        WVM->>Boltz: Continue background updates
    end

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_{Reviews (1): Last reviewed commit: "fix: gate swap claim and harden boltz fl..." | Re-trigger Greptile}