fix(chart): clear tap marker when dataset changes

LaunchedEffect(data) resets marker state so stale selection is not shown after refresh or sensor switch.

Made-with: Cursor

app/src/main/kotlin/org/db3/airmq/features/common/chart/AirMQChart.kt

@@ -13,6 +13,7 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -100,6 +101,11 @@ fun AirMQChart(
     var markerPoint: ChartDataPoint? by remember { mutableStateOf(null) }
     var showMarker by remember { mutableStateOf(false) }
 
+    LaunchedEffect(data) {
+        markerPoint = null
+        showMarker = false
+    }
+
     val sortedPoints = remember(points) {
         points.sortedBy { it.timestamp }
     }