feat(folio): show current balance on the add-transaction screen

renders the account's balance (testTag TxnCurrentBalance) below the
account name, above the credit/debit toggle, so before/after screenshots
carry comparison data.

examples/folio/app/shared/src/commonMain/kotlin/app/folio/feature/ledger/AddTransactionScreen.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -15,10 +16,12 @@ import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import app.folio.core.data.TxnType
 import app.folio.di.LocalAppGraph
+import app.folio.util.formatCents
 import app.folio.ui.BackHandler
 import app.folio.ui.component.AppButton
 import app.folio.ui.component.BackButton
 import app.folio.ui.component.ButtonStyle
+import app.folio.ui.component.Card
 import app.folio.ui.component.EmptyState
 import app.folio.ui.component.ErrorText
 import app.folio.ui.component.FieldLabel
@@ -26,6 +29,7 @@ import app.folio.ui.component.Header
 import app.folio.ui.component.Screen
 import app.folio.ui.component.Segmented
 import app.folio.ui.component.TextInput
+import app.folio.ui.theme.LocalTokens
 import app.folio.ui.theme.Type
 
 @Composable
@@ -78,10 +82,20 @@ fun AddTransactionScreen(state: AddTransactionUiState, onEvent: (AddTransactionE
             )
         },
     ) {
+        val t = LocalTokens.current
         Column(
             modifier = Modifier.fillMaxWidth().padding(vertical = 8.dp),
             verticalArrangement = Arrangement.spacedBy(16.dp),
         ) {
+            Card {
+                Text("CURRENT BALANCE", style = Type.label, color = t.textMuted)
+                Text(
+                    formatCents(state.balanceCents),
+                    style = Type.balance,
+                    color = t.text,
+                    modifier = Modifier.testTag("TxnCurrentBalance"),
+                )
+            }
             Segmented(
                 selected = if (state.type == TxnType.credit) 0 else 1,
                 labels = listOf("Credit", "Debit"),

examples/folio/app/shared/src/commonMain/kotlin/app/folio/feature/ledger/AddTransactionViewModel.kt

@@ -7,6 +7,7 @@ import app.folio.core.data.Repository
 import app.folio.core.data.TxnType
 import app.folio.navigation.Navigator
 import app.folio.navigation.Route
+import app.folio.util.balanceOf
 import app.folio.util.parseCents
 import dev.zacsweers.metro.Assisted
 import dev.zacsweers.metro.AssistedFactory
@@ -24,6 +25,7 @@ private val AMOUNT_REGEX = Regex("""^\d*(\.\d{0,2})?$""")
 
 data class AddTransactionUiState(
     val account: Account? = null,
+    val balanceCents: Long = 0,
     val type: TxnType = TxnType.credit,
     val amount: String = "",
     val note: String = "",
@@ -50,8 +52,13 @@ class AddTransactionViewModel(
     val state: StateFlow<AddTransactionUiState> = combine(
         form,
         repository.accounts.map { accounts -> accounts.firstOrNull { it.id == accountId } },
-    ) { f, account -> f.copy(account = account) }
-        .stateIn(viewModelScope, SharingStarted.Eagerly, AddTransactionUiState())
+        repository.transactions,
+    ) { f, account, transactions ->
+        f.copy(
+            account = account,
+            balanceCents = balanceOf(transactions.filter { it.accountId == accountId }),
+        )
+    }.stateIn(viewModelScope, SharingStarted.Eagerly, AddTransactionUiState())
 
     fun onEvent(event: AddTransactionEvent) {
         when (event) {