Persist LSPS2 cleanup on intercept errors

When htlc_intercepted rejects an LSPS2-owned HTLC, it fails
the intercept and prunes the per-peer and global SCID mappings
before returning an API error. Persist the peer state after
releasing locks so the cleanup survives restarts.

Author: joostjager

lightning-liquidity/src/lsps2/service.rs

@@ -1057,13 +1057,22 @@ where
 									.get_cm()
 									.fail_intercepted_htlc(intercept_id)?;
 								peer_state.remove_outbound_channel(intercept_scid);
+								let err = e.err;
 								drop(peer_state);
 								drop(outer_state_lock);
 								self.peer_by_intercept_scid
 									.write()
 									.unwrap()
 									.remove(&intercept_scid);
-								return Err(APIError::APIMisuseError { err: e.err });
+								self.persist_peer_state(counterparty_node_id).await.map_err(
+									|e| APIError::APIMisuseError {
+										err: format!(
+											"Failed to persist peer state for {}: {}",
+											counterparty_node_id, e
+										),
+									},
+								)?;
+								return Err(APIError::APIMisuseError { err });
 							},
 						}
 					} else {