qml wizard: enforce homogeneous master keys in multisig

- {xpub, Ypub, Zpub} categories cannot be mixed
- old mpk must not be used in multisig

electrum/gui/qml/components/wizard/WCHaveMasterKey.qml

@@ -42,10 +42,14 @@ WizardComponent {
 
         if (cosigner) {
             applyMasterKey(key)
-            if (wiz.hasDuplicateKeys(wizard_data)) {
+            if (wiz.hasDuplicateMasterKeys(wizard_data)) {
                 validationtext.text = qsTr('Error: duplicate master public key')
                 return false
             }
+            if (wiz.hasHeterogeneousMasterKeys(wizard_data)) {
+                validationtext.text = qsTr('Error: master public key types do not match')
+                return false
+            }
         }
 
         return valid = true

electrum/gui/qml/components/wizard/WCHaveSeed.qml

@@ -65,9 +65,12 @@ WizardComponent {
             return
         } else {
             apply()
-            if (wiz.hasDuplicateKeys(wizard_data)) {
+            if (wiz.hasDuplicateMasterKeys(wizard_data)) {
                 validationtext.text = qsTr('Error: duplicate master public key')
                 return
+            } else if (wiz.hasHeterogeneousMasterKeys(wizard_data)) {
+                validationtext.text = qsTr('Error: master public key types do not match')
+                return
             } else {
                 valid = true
             }