fix: allow DLC input signing for closed/preclosed contracts

get_signature_for_dlc_input only accepted Contract::Confirmed, causing
splice operations to fail when the referenced contract was incorrectly
moved to Closed (e.g. mempool-only splice tx treated as confirmed with
NB_CONFIRMATIONS=0). The ClosedContract struct contains the full
SignedContract data needed for signing, so the match is extended to
handle all states that carry signing data.

Author: matthewjablack

ddk-manager/src/dlc_input.rs

@@ -45,7 +45,11 @@ where
         ))?;
 
     let key_id = match contract {
-        Contract::Confirmed(c) => Ok(c.accepted_contract.offered_contract.keys_id),
+        Contract::Confirmed(c) | Contract::Signed(c) | Contract::Refunded(c) => {
+            Ok(c.accepted_contract.offered_contract.keys_id)
+        }
+        Contract::PreClosed(p) => Ok(p.signed_contract.accepted_contract.offered_contract.keys_id),
+        Contract::Closed(c) => Ok(c.signed_contract.accepted_contract.offered_contract.keys_id),
         _ => Err(Error::InvalidState(
             "Contract must be confirmed to sign DLC input.".to_string(),
         )),