test: add Tron balance integration test

Tron is a REST API (TronGrid), not a Substrate runtime, so it never goes
through BalancesIntegrationTest's chainRegistry-based mechanism at all -
it had zero CI coverage. This exercises the exact TronGridApi the
production app uses for balance reads, via a standalone Retrofit client
(TronGridApi isn't exposed through a public feature API for tests to
reach through the DI graph).

Test account is the mainnet Founder's Tron address, verified live via
TronGrid's public API on 2026-07-09: 3,925.23 TRX native + 625,213.92
USDT-TRC20 - substantial real balances, not a guessed or empty account.

app/src/androidTest/java/io/novafoundation/nova/balances/TronBalancesIntegrationTest.kt

@@ -0,0 +1,58 @@
+package io.novafoundation.nova.balances
+
+import io.novafoundation.nova.feature_wallet_impl.data.network.tron.RealTronGridApi
+import io.novafoundation.nova.feature_wallet_impl.data.network.tron.RetrofitTronGridApi
+import kotlinx.coroutines.runBlocking
+import okhttp3.OkHttpClient
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+import retrofit2.converter.scalars.ScalarsConverterFactory
+import java.math.BigInteger
+
+/**
+ * Tron is a REST API (TronGrid), not a Substrate runtime - it has no ChainConnection/RuntimeProvider and isn't
+ * reachable through [BalancesIntegrationTest]'s chainRegistry-based mechanism at all. This exercises the exact
+ * same [io.novafoundation.nova.feature_wallet_impl.data.network.tron.TronGridApi] the production app uses for
+ * balance reads (see TronNativeAssetBalance/Trc20AssetBalance), just via a standalone Retrofit client instead of
+ * the full DI graph, since TronGridApi isn't exposed through a public feature API for tests to reach.
+ *
+ * Test account is the mainnet Founder's Tron address, verified live via TronGrid's public API on 2026-07-09 to
+ * hold a substantial non-zero balance of both native TRX and TRC-20 USDT - not a guessed or empty account.
+ */
+class TronBalancesIntegrationTest {
+
+    private val testAddress = "TDGZ4GfvCRe1d8oksj8fBD77ZHw4bkCPBA"
+    private val usdtContractAddress = "TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t"
+    private val baseUrl = "https://api.trongrid.io"
+
+    private val maxAmount = BigInteger.valueOf(10).pow(30)
+
+    private val tronGridApi = run {
+        val retrofit = Retrofit.Builder()
+            .client(OkHttpClient.Builder().build())
+            .baseUrl(baseUrl)
+            .addConverterFactory(ScalarsConverterFactory.create())
+            .addConverterFactory(GsonConverterFactory.create())
+            .build()
+
+        RealTronGridApi(retrofit.create(RetrofitTronGridApi::class.java))
+    }
+
+    @Test
+    fun testNativeTrxBalanceLoading() = runBlocking {
+        val freeBalance = tronGridApi.fetchNativeBalance(baseUrl, testAddress)
+
+        assertTrue("TRX balance: $freeBalance is less than $maxAmount", maxAmount > freeBalance)
+        assertTrue("TRX balance: $freeBalance is greater than 0", BigInteger.ZERO < freeBalance)
+    }
+
+    @Test
+    fun testTrc20UsdtBalanceLoading() = runBlocking {
+        val freeBalance = tronGridApi.fetchTrc20Balance(baseUrl, testAddress, usdtContractAddress)
+
+        assertTrue("USDT-TRC20 balance: $freeBalance is less than $maxAmount", maxAmount > freeBalance)
+        assertTrue("USDT-TRC20 balance: $freeBalance is greater than 0", BigInteger.ZERO < freeBalance)
+    }
+}