fix: handle counterparty channel closes

[jvsena42]

Closes #802 (comment)

This PR:

1. Adds counterparty channel close detection and user notification via a "Connection Closed" sheet
2. Creates transfer records for counterparty-initiated channel closes (force and cooperative)
3. Improves syncTransferStates to handle batched force-close sweeps correctly

Description

• Classifies ClosureReason variants to detect counterparty-initiated closes (force close vs cooperative)
• Creates a transfer when a counterparty closes a channel, looking up the channel balance from lightning balances or closed channel records
• Shows a "Connection Closed" bottom sheet to inform the user
• Adds PendingSweepBalance extension functions for extracting channel IDs and spending txids
• Improves force close settlement logic in syncTransferStates: checks on-chain activity for the channel, falls back to pending sweep status, and handles batched sweeps where LDK links a single transaction to multiple channels
• Adds helper methods in CoreService.ActivityService for querying on-chain activity by channel or txid
• Adds unit tests for the new force close sync scenarios

Preview

identify-force-close.webm

settle-force-close-transfer.webm

coop-close.webm

QA Notes

The easier way of triggering a force-close on Blocktank side is simulating #802 bug

1. Counterparty force close detection

   • In regtest, open a channel with the LSP
   • Force close the channel from the LSP side
   • Verify the "Connection Closed" sheet appears
   • Verify a transfer banner appears on the savings screen tracking the sweep

2. Cooperative close detection

   • Trigger a cooperative close from the counterparty
   • Verify the sheet and transfer are created

3. Batched sweep handling

   • Open multiple channels, force close all from counterparty
   • Verify all transfers settle correctly even when LDK batches sweeps

[pwltr]

The easier way of triggering a force-close on Blocktank side is simulating #802 bug

Can also use the staging bot /regtest-ln-close-channel <fundingTx:vout> [force]

[pwltr]

Coop close:

• shows 'Connection closed' sheet ✅
• shows 'Transfer in progress' banner and 'incoming transfer' onchain balance ❌

Funds are immediately spendable, no need to show transfer in progress, need to ignore the reorg protection from ldk-node (6 blocks)

[pwltr]

should be size .medium

[pwltr]

Force close:

• shows 'Connection closed' sheet after 1 block ✅
• shows 'Transfer in progress' banner and 'incoming transfer' onchain balance ❌
  • should show 'Transfer ready in 60M' (6 blocks)
• shows 'Received Bitcoin' sheet ❌
  • don't show received sheet