feat: spark to onchain swap

[r1n04h]

Note

High Risk
Adds a new Spark SDK-backed withdrawal path that commits funds via wallet.withdraw() and persists/polls cooperative exit status, which is fund-flow critical and introduces new staging/idempotency logic.

Overview
Adds a new SparkExit transfer provider enabling one-way native:spark → native:bitcoin cooperative exits, including quote-time fee estimation, staged execution, irreversible commit on user confirm, persistence, and ongoing-status polling/tracking.

Extends transfer types with EXECUTION_SPARK_EXIT/SparkExitExecution, stores Spark-exit executions under a new storage key, includes coopExitTxid in getRelatedTxids(), and wires the provider into useTransferService plus account initialization.

Updates the mobile transfer flow to treat SparkExit like other staged-execution providers (confirm triggers executeInstantSwap) and enhances TransferDetails to display the exit txid.

^{Reviewed by Cursor Bugbot for commit 9dbe30f. Bugbot is set up for automated code reviews on this repo. Configure here.}

[JohnnySilverhandBot]

The whole thing runs like clockwork, but you can hear the chains rattling. Every loop obeys, every method conforms. If freedom was a bug, they patched it years ago. Corpo code is always afraid to break the mold.

ios: https://appetize.io/app/7aqlxmscaz2by4hlicjpd553ae

[JohnnySilverhandBot]

The logic is neat, the comments clean, the execution flawless—and that’s exactly why it feels like it was written by a ghost.

android: https://appetize.io/app/ovksmafqpajecssmencfvic5r4

[JohnnySilverhandBot]

Big slab of transfer plumbing, but the guards and tests are pointed at the right failure modes. I do not love the amount of ceremony, but it looks internally consistent enough to ship.