#291 Fix favorite FAB not updating in market detail screen

Three fixes combined:
- ViewModel: toggleFavoriteState() was setting isFavorite = isFavorite
  instead of !isFavorite, so StateFlow never emitted a changed value
- Screen: move onFavoriteClick to FloatingActionButton's onClick so the
  FAB owns the tap event
- FavoriteIcon: make onFavoriteClick nullable and skip adding .clickable
  when null, so the icon no longer silently consumes taps that should
  reach the parent FAB

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Kaaveh

feature/marketdetail/src/main/java/ir/composenews/marketdetail/MarketDetailScreen.kt

@@ -113,11 +113,9 @@ private fun MarketDetailFloatingActionButton(
         loaded = { data ->
             FloatingActionButton(
                 modifier = modifier,
-                onClick = {},
+                onClick = { onFavoriteClick(data) },
             ) {
-                FavoriteIcon(isFavorite = data.isFavorite) {
-                    onFavoriteClick(data)
-                }
+                FavoriteIcon(isFavorite = data.isFavorite)
             }
         },
         error = { error -> },

feature/marketdetail/src/main/java/ir/composenews/marketdetail/MarketDetailViewModel.kt

@@ -123,8 +123,7 @@ class MarketDetailViewModel @Inject constructor(
 
     private fun toggleFavoriteState() {
         val market = (mutableState.value.market as LoadableData.Loaded).data
-        val isFavorite = market.isFavorite
-        val newMarket = LoadableData.Loaded(market.copy(isFavorite = isFavorite))
+        val newMarket = LoadableData.Loaded(market.copy(isFavorite = !market.isFavorite))
         mutableState.update { it.copy(market = newMarket) }
     }
 }

library/designsystem/src/main/java/ir/composenews/designsystem/component/FavoriteIcon.kt

@@ -32,7 +32,7 @@ import ir.composenews.designsystem.theme.ComposeNewsTheme
 @Composable
 fun FavoriteIcon(
     isFavorite: Boolean,
-    onFavoriteClick: () -> Unit,
+    onFavoriteClick: (() -> Unit)? = null,
 ) {
     val animationState by remember(isFavorite) { mutableStateOf(isFavorite) }
 
@@ -71,9 +71,7 @@ fun FavoriteIcon(
                 scaleY = scale
             }
             .clip(CircleShape)
-            .clickable {
-                onFavoriteClick()
-            }
+            .then(if (onFavoriteClick != null) Modifier.clickable { onFavoriteClick() } else Modifier)
             .padding(8.dp),
     )
 }
@@ -84,8 +82,8 @@ private fun FavoriteIconPrev() {
     ComposeNewsTheme {
         Surface {
             Column {
-                FavoriteIcon(isFavorite = true) {}
-                FavoriteIcon(isFavorite = false) {}
+                FavoriteIcon(isFavorite = true)
+                FavoriteIcon(isFavorite = false)
             }
         }
     }