staticaddr/loopin: use generated change addresses

Create a fresh static change address for fractional loop-ins and persist
its key locator with the selected HTLC outpoint. Recovery reconstructs
the same change output instead of returning funds to the legacy root
address.

loopdb/sqlc/models.go

@@ -152,6 +152,10 @@ type StaticAddressSwap struct {
 	Fast                         bool
 	ConfirmationRiskDecision     string
 	ConfirmationRiskDecisionTime sql.NullTime
+	ChangeStaticAddressID        sql.NullInt32
+	ConfirmedHtlcTxID            sql.NullString
+	ConfirmedHtlcOutputIndex     sql.NullInt32
+	ConfirmedHtlcOutputValue     sql.NullInt64
 }
 
 type StaticAddressSwapUpdate struct {