Add read-only Tron (TRC20) chain family support (#9)

* Add read-only Tron (TRC20) chain family support

Adds Tron as a third chain family alongside Substrate and EVM:
address derivation (BIP44 coin type 195, secp256k1 reused from the
existing Ethereum path, Base58Check encoding), TronGrid-backed TRX
and TRC20 USDT balance display, and a Room migration for the new
per-account Tron key/address columns. Read-only only — no send,
signing, or broadcast support yet.

* fix: exhaustive when branches for Trc20/TronNative asset types

ChainExt.kt's onChainAssetId and Common.kt's existentialDepositError
both switch exhaustively over Chain.Asset.Type and didn't have cases
for the new Trc20/TronNative variants, breaking compilation. Trc20
mirrors EvmErc20 (contract address as the on-chain id, dust burns
rather than transfers on removal); TronNative mirrors EvmNative.

core-db/src/androidTest/java/io/novafoundation/nova/core_db/dao/Helpers.kt

@@ -57,6 +57,7 @@ fun chainOf(
     legacyPrefix = null,
     isTestNet = false,
     isEthereumBased = false,
+    isTronBased = false,
     hasCrowdloans = false,
     additional = "",
     governance = "governance",

core-db/src/main/java/io/novafoundation/nova/core_db/AppDatabase.kt

@@ -94,6 +94,7 @@ import io.novafoundation.nova.core_db.migrations.AddStakingTypeToTotalRewards_44
 import io.novafoundation.nova.core_db.migrations.AddSwapOption_48_49
 import io.novafoundation.nova.core_db.migrations.AddTransactionVersionToRuntime_50_51
 import io.novafoundation.nova.core_db.migrations.AddTransferApisTable_29_30
+import io.novafoundation.nova.core_db.migrations.AddTronSupport_73_74
 import io.novafoundation.nova.core_db.migrations.AddTypeExtrasToMetaAccount_68_69
 import io.novafoundation.nova.core_db.migrations.AddVersioningToGovernanceDapps_32_33
 import io.novafoundation.nova.core_db.migrations.AddWalletConnectSessions_39_40
@@ -166,7 +167,7 @@ import io.novafoundation.nova.core_db.model.operation.SwapTypeLocal
 import io.novafoundation.nova.core_db.model.operation.TransferTypeLocal
 
 @Database(
-    version = 73,
+    version = 74,
     entities = [
         AccountLocal::class,
         NodeLocal::class,
@@ -271,6 +272,7 @@ abstract class AppDatabase : RoomDatabase() {
                     .addMigrations(AddFavoriteDAppsOrdering_65_66, AddLegacyAddressPrefix_66_67, AddSellProviders_67_68)
                     .addMigrations(AddTypeExtrasToMetaAccount_68_69, AddMultisigCalls_69_70, AddMultisigSupportFlag_70_71)
                     .addMigrations(AddGifts_71_72, AddFieldsToContributions)
+                    .addMigrations(AddTronSupport_73_74)
                     .build()
             }
             return instance!!

core-db/src/main/java/io/novafoundation/nova/core_db/migrations/73_74_AddTronSupport.kt

@@ -0,0 +1,14 @@
+package io.novafoundation.nova.core_db.migrations
+
+import androidx.room.migration.Migration
+import androidx.sqlite.db.SupportSQLiteDatabase
+
+val AddTronSupport_73_74 = object : Migration(73, 74) {
+
+    override fun migrate(db: SupportSQLiteDatabase) {
+        db.execSQL("ALTER TABLE chains ADD COLUMN isTronBased INTEGER NOT NULL DEFAULT 0")
+
+        db.execSQL("ALTER TABLE meta_accounts ADD COLUMN tronPublicKey BLOB")
+        db.execSQL("ALTER TABLE meta_accounts ADD COLUMN tronAddress BLOB")
+    }
+}

core-db/src/main/java/io/novafoundation/nova/core_db/model/chain/ChainLocal.kt

@@ -21,6 +21,8 @@ data class ChainLocal(
     val prefix: Int,
     val legacyPrefix: Int?,
     val isEthereumBased: Boolean,
+    @ColumnInfo(defaultValue = "0")
+    val isTronBased: Boolean,
     val isTestNet: Boolean,
     @ColumnInfo(defaultValue = "1")
     val hasSubstrateRuntime: Boolean,

core-db/src/main/java/io/novafoundation/nova/core_db/model/chain/account/MetaAccountLocal.kt

@@ -36,7 +36,9 @@ class MetaAccountLocal(
     @ColumnInfo(defaultValue = "ACTIVE")
     val status: Status,
     val globallyUniqueId: String,
-    val typeExtras: SerializedJson?
+    val typeExtras: SerializedJson?,
+    val tronPublicKey: ByteArray? = null,
+    val tronAddress: ByteArray? = null,
 ) {
 
     enum class Status {
@@ -54,6 +56,9 @@ class MetaAccountLocal(
             const val ETHEREUM_PUBKEY = "ethereumPublicKey"
             const val ETHEREUM_ADDRESS = "ethereumAddress"
 
+            const val TRON_PUBKEY = "tronPublicKey"
+            const val TRON_ADDRESS = "tronAddress"
+
             const val NAME = "name"
             const val IS_SELECTED = "isSelected"
             const val POSITION = "position"
@@ -83,7 +88,9 @@ class MetaAccountLocal(
             type = type,
             status = status,
             globallyUniqueId = globallyUniqueId,
-            typeExtras = typeExtras
+            typeExtras = typeExtras,
+            tronPublicKey = tronPublicKey,
+            tronAddress = tronAddress
         ).also {
             it.id = id
         }
@@ -100,6 +107,8 @@ class MetaAccountLocal(
         if (!substrateAccountId.contentEquals(other.substrateAccountId)) return false
         if (!ethereumPublicKey.contentEquals(other.ethereumPublicKey)) return false
         if (!ethereumAddress.contentEquals(other.ethereumAddress)) return false
+        if (!tronPublicKey.contentEquals(other.tronPublicKey)) return false
+        if (!tronAddress.contentEquals(other.tronAddress)) return false
         if (name != other.name) return false
         if (parentMetaId != other.parentMetaId) return false
         if (isSelected != other.isSelected) return false
@@ -119,6 +128,8 @@ class MetaAccountLocal(
         result = 31 * result + (substrateAccountId?.contentHashCode() ?: 0)
         result = 31 * result + (ethereumPublicKey?.contentHashCode() ?: 0)
         result = 31 * result + (ethereumAddress?.contentHashCode() ?: 0)
+        result = 31 * result + (tronPublicKey?.contentHashCode() ?: 0)
+        result = 31 * result + (tronAddress?.contentHashCode() ?: 0)
         result = 31 * result + name.hashCode()
         result = 31 * result + (parentMetaId?.hashCode() ?: 0)
         result = 31 * result + isSelected.hashCode()