feat(send): improve Lightning send failure recovery

[pwltr]

Description

Ports the iOS Lightning send-failure retry/support behavior to Android.

• Shows the send failure screen for failed Lightning sends instead of relying only on toasts.
• Maps LDK payment failure reasons to localized, user-facing strings and avoids exposing internal error values like Optional(...), NodeError, or DuplicatePayment.
• Uses the reusable generic route failure copy for routeNotFound and retriesExhausted.
• Preserves LDK failure reasons for payments that first enter SendPendingScreen and fail later.
• Shows the correct failure title for Lightning vs on-chain send errors.
• Shows Contact Support above Try Again on the Lightning send failure screen.
• Prefills the support report with failure type, payment method, routing cache reset status, and the available Lightning payment request.
• Resets routing caches only for routing-related failures, and only once per current send flow/payment attempt.
• Retries non-routing failures normally without resetting graph/scorer caches.
• Retry clears local/VSS network graph data and scorer/pathfinding score data before restarting ldk-node when a routing reset is needed.
• Retry waits for local routing data to be usable again without requiring a newer remote RGS snapshot timestamp or waiting only on delayed graph-cache persistence.
• Guards retry state in WalletViewModel so overlapping retry flows cannot surface stale timeout errors.
• Resets send navigation back to the retry route instead of stacking retry screens on top of the failure screen.

Closes #829

Preview

Normal payment:

Screen.Recording.2026-08-11.at.17.59.27.mov

QuickPay:

Screen.Recording.2026-08-12.at.14.55.13.mov

QA Notes

Tested on mainnet emulator:

• Confirmed ROUTE_NOT_FOUND surfaces user-facing payment failure copy.
• Confirmed pending RETRIES_EXHAUSTED failures surface the localized retries-exhausted copy instead of generic failure copy.
• Confirmed Try Again deletes local graph, VSS graph, scorer, and external scores cache for the first routing-related retry.
• Confirmed Try Again does not repeat routing cache reset after a reset has already been attempted in the current send flow.
• Confirmed retry restarts from an empty graph and accepts the same RGS snapshot timestamp.
• Confirmed retry waits through RGS/scorer refresh and returns to the send confirmation path without timing out when graph cache persistence lags behind the in-memory graph.
• Confirmed no stale retry timeout after repeated retry attempts.

Automated checks:

• compileDevDebugKotlin
• PaymentFailureReasonExtTest.kt
• AppViewModelSendFlowTest.kt
• detekt

[greptile-apps]

Greptile Summary

The PR replaces toast-only Lightning send failures with a recoverable failure screen, localized failure reasons, support-report prefilling, and routing-cache resets for routing-related retries.

• Propagates typed LDK payment failure reasons through normal, pending, and QuickPay send flows.
• Adds retry-route and reset-attempt state to the nested send navigation graph.
• Clears graph and scorer caches, restarts LDK, and waits for routing sources before retrying.
• Adds localized failure and support copy plus focused send-flow tests.

Confidence Score: 4/5

The PR should not merge until pending QuickPay failures can retry without crashing from cleared payment state.

The new Pending branch clears the only QuickPay request state, while the corresponding failure route explicitly returns to a destination that requires that state to be non-null.

Files Needing Attention: app/src/main/java/to/bitkit/ui/screens/wallets/send/SendQuickPayScreen.kt, app/src/main/java/to/bitkit/ui/sheets/SendSheet.kt

Important Files Changed

Filename	Overview
app/src/main/java/to/bitkit/ui/screens/wallets/send/SendQuickPayScreen.kt	Moves QuickPay cleanup to terminal results, but clearing state on Pending breaks the newly added pending-failure retry route.
app/src/main/java/to/bitkit/ui/sheets/SendSheet.kt	Adds typed failure navigation, support reporting, and routing-aware retry behavior; its QuickPay retry destination still requires state that the Pending path clears.
app/src/main/java/to/bitkit/repositories/LightningRepo.kt	Adds graph/scorer cache reset and bounded routing-data refresh orchestration without an independently established defect.
app/src/main/java/to/bitkit/viewmodels/AppViewModel.kt	Routes active Lightning failures into the send sheet and preserves typed failure details and payment requests.
app/src/main/java/to/bitkit/viewmodels/WalletViewModel.kt	Serializes routing-reset retries with a mutex and exposes retry progress to the UI.
app/src/main/java/to/bitkit/ext/PaymentFailureReasonExt.kt	Maps LDK failure reasons to localized user copy and sanitized compact support metadata.

Sequence Diagram

sequenceDiagram
    participant User
    participant QuickPay as QuickPay Screen
    participant AppVM as AppViewModel
    participant Pending as Pending Screen
    participant Error as Failure Screen

    QuickPay->>AppVM: resetQuickPay()
    QuickPay->>Pending: "navigate with retryRoute=QuickPay"
    Pending-->>Error: payment failure
    User->>Error: Try Again
    Error->>QuickPay: clear stack and navigate
    QuickPay->>AppVM: read quickPayData
    AppVM-->>QuickPay: null
    QuickPay--xQuickPay: requireNotNull crashes

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