fix(apple): stop delete confirmation re-presenting on macOS

Confirming a transfer/history deletion flashed the same confirmation alert a
second time before it went away. The destructive button runs confirmDelete
synchronously (setting isDeleting = true), while the alert's isPresented
dismiss binding fires asynchronously and then no-ops because its
`if !isDeleting` guard is already false — leaving the open flag set, so macOS
re-reads the binding as true and re-presents the alert until the async delete
finally clears it.

Close the confirmation flag synchronously in confirmDeleteTransfer /
confirmHistoryDelete so there's no window for re-presentation. Tests assert
the flag clears immediately, before the async delete completes.

apple/Tests/ReceiveModelTests.swift

@@ -24,6 +24,9 @@ final class ReceiveModelTests: XCTestCase {
 		XCTAssertEqual(model.state.historyDeleteTarget, .transfer(transferId: 5))
 
 		model.confirmHistoryDelete()
+		// Must close immediately (not after the async delete) so the alert can't
+		// re-present on macOS.
+		XCTAssertNil(model.state.historyDeleteTarget)
 		await waitUntil { core.deletedTransfers.contains(5) }
 		XCTAssertEqual(core.deletedTransfers, [5])
 		XCTAssertNil(model.state.historyDeleteTarget)

apple/Tests/SendModelTests.swift

@@ -32,6 +32,9 @@ final class SendModelTests: XCTestCase {
 		XCTAssertTrue(model.state.isDeleteConfirmationOpen)
 
 		model.confirmDeleteTransfer()
+		// Must close immediately (not after the async delete) so the alert can't
+		// re-present on macOS.
+		XCTAssertFalse(model.state.isDeleteConfirmationOpen)
 		await waitUntil { core.deletedTransfers.contains(3) }
 		XCTAssertEqual(core.deletedTransfers, [3])
 		XCTAssertNil(model.state.selectedTransferId)