fix: Tron transfers signed with the wrong key (or crashed) due to missing multi-chain-encryption case

SecretsSigner.multiChainEncryptionFor() only recognized substrate accounts, standard
Ethereum accounts, and explicit per-chain override accounts. A Tron account's accountId
matches none of those (same secp256k1 scheme as Ethereum, but a different SLIP-44 derivation
path/keypair), so it fell through to null and crashed on the `!!` - found live testing the
send flow end-to-end, reproduced on every Confirm tap.

Fixing just the null case would have signed Tron transfers with the Ethereum keypair
instead of the Tron one (getMetaAccountKeypair only distinguished ethereum/substrate),
producing an invalid signature. Threaded a proper isTronBased flag through
down to mapMetaAccountSecretsToKeypair so Tron gets its own MetaAccountSecrets.TronKeypair.

common/src/main/java/io/novafoundation/nova/common/data/secrets/v2/SecretStoreV2.kt

@@ -156,20 +156,25 @@ val AccountSecrets.isChainAccountSecrets
 suspend fun SecretStoreV2.getMetaAccountKeypair(
     metaId: Long,
     isEthereum: Boolean,
+    isTron: Boolean = false,
 ): Keypair = withContext(Dispatchers.Default) {
     val secrets = getMetaAccountSecrets(metaId) ?: noMetaSecrets(metaId)
 
-    mapMetaAccountSecretsToKeypair(secrets, isEthereum)
+    mapMetaAccountSecretsToKeypair(secrets, isEthereum, isTron)
 }
 
 fun mapMetaAccountSecretsToKeypair(
     secrets: EncodableStruct<MetaAccountSecrets>,
     ethereum: Boolean,
+    tron: Boolean = false,
 ): Keypair {
-    val keypairStruct = if (ethereum) {
-        secrets[MetaAccountSecrets.EthereumKeypair] ?: noEthereumSecret()
-    } else {
-        secrets[MetaAccountSecrets.SubstrateKeypair]
+    // Tron reuses Ethereum's secp256k1 curve but derives its own keypair under a different SLIP-44 path - it
+    // must be checked before `ethereum`, not folded into it, or a Tron account would get signed with the
+    // wrong (Ethereum) private key.
+    val keypairStruct = when {
+        tron -> secrets[MetaAccountSecrets.TronKeypair] ?: noTronSecret()
+        ethereum -> secrets[MetaAccountSecrets.EthereumKeypair] ?: noEthereumSecret()
+        else -> secrets[MetaAccountSecrets.SubstrateKeypair]
     }
 
     return mapKeypairStructToKeypair(keypairStruct)
@@ -198,6 +203,8 @@ private fun noChainSecrets(metaId: Long, accountId: ByteArray): Nothing {
 
 private fun noEthereumSecret(): Nothing = error("No ethereum keypair found")
 
+private fun noTronSecret(): Nothing = error("No tron keypair found")
+
 fun mapKeypairStructToKeypair(struct: EncodableStruct<KeyPairSchema>): Keypair {
     return Keypair(
         publicKey = struct[KeyPairSchema.PublicKey],

feature-account-impl/src/main/java/io/novafoundation/nova/feature_account_impl/data/signer/secrets/SecretsSigner.kt

@@ -142,11 +142,13 @@ class SecretsSigner(
     private suspend fun getKeypair(accountId: AccountId): Keypair {
         val chainsById = chainRegistry.chainsById()
         val multiChainEncryption = metaAccount.multiChainEncryptionFor(accountId, chainsById)!!
+        val isTronBased = metaAccount.tronAddress?.contentEquals(accountId) == true
 
         return secretStoreV2.getKeypair(
             metaAccount = metaAccount,
             accountId = accountId,
-            isEthereumBased = multiChainEncryption is MultiChainEncryption.Ethereum
+            isEthereumBased = multiChainEncryption is MultiChainEncryption.Ethereum,
+            isTronBased = isTronBased
         )
     }
 
@@ -159,11 +161,12 @@ class SecretsSigner(
     private suspend fun SecretStoreV2.getKeypair(
         metaAccount: MetaAccount,
         accountId: AccountId,
-        isEthereumBased: Boolean
+        isEthereumBased: Boolean,
+        isTronBased: Boolean = false,
     ) = if (hasChainSecrets(metaAccount.id, accountId)) {
         getChainAccountKeypair(metaAccount.id, accountId)
     } else {
-        getMetaAccountKeypair(metaAccount.id, isEthereumBased)
+        getMetaAccountKeypair(metaAccount.id, isEthereumBased, isTronBased)
     }
 
     /**
@@ -173,6 +176,10 @@ class SecretsSigner(
         return when {
             substrateAccountId.contentEquals(accountId) -> substrateCryptoType?.let(MultiChainEncryption.Companion::substrateFrom)
             ethereumAccountId().contentEquals(accountId) -> MultiChainEncryption.Ethereum
+            // Tron reuses the exact same secp256k1 signing scheme as Ethereum - it just has its own accountId
+            // (different SLIP-44 derivation path), so it doesn't match ethereumAccountId() above and was
+            // falling through to the chainAccounts lookup, which doesn't cover it either -> null -> NPE on `!!`.
+            tronAddress?.contentEquals(accountId) == true -> MultiChainEncryption.Ethereum
             else -> {
                 val chainAccount = chainAccounts.values.firstOrNull { it.accountId.contentEquals(accountId) } ?: return null
                 val cryptoType = chainAccount.cryptoType ?: return null