fix: TRC-20 balance always read 0 for never-activated holders

Trc20AssetBalance/RealTronGridApi.fetchTrc20Balance() read through
TronGrid's /v1/accounts/{address} REST endpoint - but a TRC-20 balance
lives entirely in the token contract's own storage, not the holder's
Account object. An address that has only ever received TRC-20 tokens
(never native TRX, never otherwise "activated" on-chain) has no Account
object at all, so /v1/accounts silently returns `data: []` for it
regardless of its real token balance, and the old code treated that the
same as a genuinely empty/zero account.

Found via a live test: a real wallet received 5 USDT-TRC20, the exchange
confirmed the transfer complete on-chain, but the app kept showing 0.
Independently verified live: /v1/accounts returned empty for the address,
while a direct balanceOf(address) contract call (triggerconstantcontract)
correctly returned 5000000.

Rewrote fetchTrc20Balance() to read via balanceOf(address) instead -
reuses the existing triggerConstantContract() call already used for TRC-20
transfer fee estimation, plus a new encodeBalanceOfParameters() ABI helper
alongside the existing transfer() one. Added a regression test pinned to
this exact real address/balance so this can't silently regress again.

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

@@ -1,5 +1,6 @@
 package io.novafoundation.nova.balances
 
+import io.novafoundation.nova.common.utils.tronAddressToAccountId
 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.delay
@@ -29,6 +30,14 @@ class TronBalancesIntegrationTest {
     private val usdtContractAddress = "TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t"
     private val baseUrl = "https://api.trongrid.io"
 
+    // A real wallet that received exactly 5 USDT-TRC20 (2026-07-11) and has NEVER had any native TRX/other
+    // on-chain activity - confirmed live to have no Account object at all (`/v1/accounts` returns `data: []`)
+    // despite genuinely holding the token (`balanceOf` correctly returns 5000000). Regression coverage for the
+    // exact bug this uncovered: fetchTrc20Balance used to read through `/v1/accounts` and silently returned 0
+    // for any address in this state, well after it was live and had already deceived a real user mid-transfer.
+    private val unactivatedHolderAddress = "TUdvwdGeqcag51XkhgRK21KmhH2qw37LZG"
+    private val unactivatedHolderExpectedUsdtBalance = BigInteger.valueOf(5_000_000L)
+
     private val maxAmount = BigInteger.valueOf(10).pow(30)
 
     private val tronGridApi = run {
@@ -68,9 +77,21 @@ class TronBalancesIntegrationTest {
 
     @Test
     fun testTrc20UsdtBalanceLoading() = runBlocking {
-        val freeBalance = retryOn429 { tronGridApi.fetchTrc20Balance(baseUrl, testAddress, usdtContractAddress) }
+        val freeBalance = retryOn429 { tronGridApi.fetchTrc20Balance(baseUrl, testAddress.tronAddressToAccountId(), usdtContractAddress) }
 
         assertTrue("USDT-TRC20 balance: $freeBalance is less than $maxAmount", maxAmount > freeBalance)
         assertTrue("USDT-TRC20 balance: $freeBalance is greater than 0", BigInteger.ZERO < freeBalance)
     }
+
+    @Test
+    fun testTrc20BalanceLoadingForNeverActivatedHolder() = runBlocking {
+        val freeBalance = retryOn429 {
+            tronGridApi.fetchTrc20Balance(baseUrl, unactivatedHolderAddress.tronAddressToAccountId(), usdtContractAddress)
+        }
+
+        assertTrue(
+            "USDT-TRC20 balance for a never-activated holder: expected $unactivatedHolderExpectedUsdtBalance, got $freeBalance",
+            freeBalance == unactivatedHolderExpectedUsdtBalance
+        )
+    }
 }