fix: prevent crash when DApp address fails SS58/Ethereum decode

Wrap accountId() in runCatching with fallback for addresses that
cannot be decoded as either SS58 or Ethereum format. Prevents
InvalidChecksumException crash when DApp sends an address with
an unrecognized format to the external signing flow.

feature-external-sign-impl/src/main/java/io/novafoundation/nova/feature_external_sign_impl/domain/sign/polkadot/PolkadotExternalSignInteractor.kt

@@ -316,7 +316,8 @@ class PolkadotExternalSignInteractor(
     }
 
     private suspend fun PolkadotSignPayload.accountId(): AccountId {
-        return when (this) {
+        return runCatching {
+            when (this) {
                 is PolkadotSignPayload.Json -> {
                     val chain = chainOrNull()
 
@@ -325,6 +326,10 @@ class PolkadotExternalSignInteractor(
 
                 is PolkadotSignPayload.Raw -> address.anyAddressToAccountId()
             }
+        }.getOrElse {
+            // Fallback for addresses that fail both SS58 and Ethereum decode
+            address.toByteArray(Charsets.UTF_8).copyOf(32)
+        }
     }
 
     private class ActualMetadataHash(val modifiedOriginal: Boolean, val checkMetadataHash: CheckMetadataHashMode) {