add seedsigner to wallet import list

src/main/java/com/sparrowwallet/sparrow/control/WalletImportDialog.java

@@ -48,7 +48,7 @@ public class WalletImportDialog extends Dialog<Wallet> {
         AnchorPane.setRightAnchor(scrollPane, 0.0);
 
         importAccordion = new Accordion();
-        List<KeystoreFileImport> keystoreImporters = List.of(new ColdcardSinglesig(), new CoboVaultSinglesig(), new KeystoneSinglesig(), new PassportSinglesig(), new GordianSeedTool(), new SpecterDIY());
+        List<KeystoreFileImport> keystoreImporters = List.of(new ColdcardSinglesig(), new CoboVaultSinglesig(), new KeystoneSinglesig(), new PassportSinglesig(), new GordianSeedTool(), new SeedSigner(), new SpecterDIY());
         for(KeystoreFileImport importer : keystoreImporters) {
             FileWalletKeystoreImportPane importPane = new FileWalletKeystoreImportPane(importer);
             importAccordion.getPanes().add(importPane);

src/main/java/com/sparrowwallet/sparrow/io/SeedSigner.java

@@ -17,4 +17,9 @@ public class SeedSigner extends SpecterDIY {
     public WalletModel getWalletModel() {
         return WalletModel.SEEDSIGNER;
     }
+
+    @Override
+    public boolean isFileFormatAvailable() {
+        return false;
+    }
 }