Apply theme colors to TopAppBar and remove LazyListState

This commit updates the `DiffCheckerScreen.kt` to apply theme colors to the `TopAppBar`. Specifically, the `containerColor` is set to `Color.White` and `titleContentColor` to `primary`.

Additionally, the `rememberLazyListState` instances (`scrollStateOld` and `scrollStateNew`) have been removed from `CharDiffText.kt` as they were not being used to synchronize scrolling between the two `LazyColumn`s.

Author: JahidHasanCO

app/src/main/java/dev/jahidhasanco/diffly/presentation/component/CharDiffText.kt

@@ -11,7 +11,6 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
-import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
@@ -27,12 +26,8 @@ import dev.jahidhasanco.diffly.presentation.theme.delete
 
 @Composable
 fun CharDiffText(diffResult: List<DiffEntry>) {
-    val scrollStateOld = rememberLazyListState()
-    val scrollStateNew = rememberLazyListState()
-
     Row(modifier = Modifier.fillMaxSize()) {
         LazyColumn(
-            state = scrollStateOld,
             modifier = Modifier
                 .weight(1f)
                 .fillMaxHeight()
@@ -79,7 +74,6 @@ fun CharDiffText(diffResult: List<DiffEntry>) {
 
         // New text column
         LazyColumn(
-            state = scrollStateNew,
             modifier = Modifier
                 .weight(1f)
                 .fillMaxHeight()

app/src/main/java/dev/jahidhasanco/diffly/presentation/screen/DiffCheckerScreen.kt

@@ -22,6 +22,7 @@ import androidx.compose.material3.SwitchDefaults
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextFieldDefaults
 import androidx.compose.material3.TopAppBar
+import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -47,11 +48,18 @@ fun DiffCheckerScreen(viewModel: MainViewModel) {
 
     Scaffold(
         modifier = Modifier
-            .fillMaxSize()
-            .background(background),
+            .fillMaxSize(),
+        containerColor = background,
         topBar = {
             TopAppBar(
-                title = { Text("Diffly") },
+                title = {
+                    Text("Diffly")
+                },
+
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = Color.White,
+                    titleContentColor = primary
+                ),
             )
         }) { innerPadding ->
         Column(