fix(player): keep seek bar thumb at target on release

Previously, the Slider's value was switched from the local sliderPosition to
the positionMs prop the instant onValueChangeFinished cleared isScrubbing.
Because the prop had not yet caught up with the committed seek, the thumb
visibly snapped back to the pre-seek position before jumping to the target.

Drive the slider from sliderPosition unconditionally, sync sliderPosition
from the prop via a LaunchedEffect only when not scrubbing, and pin
sliderPosition to the committed target before clearing isScrubbing in
onValueChangeFinished.

app/src/main/java/hu/bbara/purefin/ui/screen/player/components/PlayerSeekBar.kt

@@ -8,6 +8,7 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.Slider
 import androidx.compose.material3.SliderDefaults
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableStateOf
@@ -33,7 +34,16 @@ fun PlayerSeekBar(
     val currentPosition = positionMs.coerceIn(0, safeDuration)
     var sliderPosition by remember { mutableFloatStateOf(currentPosition.toFloat()) }
     var isScrubbing by remember { mutableStateOf(false) }
-    val sliderValue = if (isScrubbing) sliderPosition else currentPosition.toFloat()
+    val sliderValue = sliderPosition
+
+    // Keep sliderPosition in sync with the player's position when the user is not
+    // actively scrubbing. While scrubbing, the local drag value is preserved so the
+    // thumb does not snap back to a stale positionMs prop before the seek is committed.
+    LaunchedEffect(positionMs) {
+        if (!isScrubbing) {
+            sliderPosition = positionMs.toFloat()
+        }
+    }
 
     Box(
         modifier = modifier
@@ -64,6 +74,7 @@ fun PlayerSeekBar(
             },
             onValueChangeFinished = {
                 val targetPosition = sliderPosition.toLong().coerceIn(0L, safeDuration)
+                sliderPosition = targetPosition.toFloat()
                 isScrubbing = false
                 onSeek(targetPosition)
             },