feat: clean input when focus change

Author: jvsena42

app/src/main/java/to/bitkit/ui/screens/widgets/calculator/components/CalculatorCard.kt

@@ -22,6 +22,7 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.focus.onFocusChanged
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.res.painterResource
@@ -114,7 +115,9 @@ fun CalculatorCardContent(
 
             // Bitcoin input with visual transformation
             CalculatorInput(
-                modifier = Modifier.fillMaxWidth(),
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .onFocusChanged { focusState -> if (focusState.hasFocus) onBtcChange("") },
                 value = btcValue,
                 onValueChange = onBtcChange,
                 currencySymbol = BITCOIN_SYMBOL,
@@ -126,7 +129,9 @@ fun CalculatorCardContent(
 
             // Fiat input with decimal transformation
             CalculatorInput(
-                modifier = Modifier.fillMaxWidth(),
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .onFocusChanged { focusState -> if (focusState.hasFocus) onFiatChange("") },
                 value = fiatValue,
                 onValueChange = onFiatChange,
                 currencySymbol = fiatSymbol,