fix: unnecessary stubbing + missing assertTrue import in Tron backfill test

@Before's preferences.getBoolean stub was never invoked by migrate()-only
tests (only migrationNeeded() reads that preference), tripping Mockito's
strict-stubs UnnecessaryStubbingException across the whole class. Moved
it into a dedicated migrationNeeded() test, matched via any() rather than
the production class's private preference-key constant (which isn't
visible here), and added the missing assertTrue import.

feature-account-impl/src/test/java/io/novafoundation/nova/feature_account_impl/data/repository/datasource/migration/TronAddressBackfillMigrationTest.kt

@@ -17,6 +17,7 @@ import io.novasama.substrate_sdk_android.encrypt.json.JsonDecoder
 import io.novasama.substrate_sdk_android.encrypt.mnemonic.MnemonicCreator
 import io.novasama.substrate_sdk_android.scale.EncodableStruct
 import kotlinx.coroutines.runBlocking
+import org.junit.Assert.assertTrue
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -79,10 +80,18 @@ class TronAddressBackfillMigrationTest {
         // Real factory, not a mock - the whole point of this test is to exercise the actual derivation.
         val accountSecretsFactory = AccountSecretsFactory(jsonDecoder)
         subject = TronAddressBackfillMigration(preferences, secretStoreV2, metaAccountDao, accountSecretsFactory)
+    }
 
-        // any() would try to unbox a null placeholder into the primitive Boolean parameter and crash - Mockito's
+    @Test
-        // own anyBoolean() returns a real `false` default instead, avoiding that entirely.
+    fun `migrationNeeded should reflect the persisted flag`(): Unit = runBlocking {
+        // The flag's preference key is a private implementation detail of the production class - matched via
+        // any() here rather than duplicating the literal key string, which would let this test pass even if
+        // that string silently drifted out of sync with the production code.
         whenever(preferences.getBoolean(any(), Mockito.anyBoolean())).thenReturn(false)
+        assertTrue(subject.migrationNeeded())
+
+        whenever(preferences.getBoolean(any(), Mockito.anyBoolean())).thenReturn(true)
+        assertTrue(!subject.migrationNeeded())
     }
 
     @Test