fix(ui): align back arrows with the search bar leading icon

Use one shared back button with a 28dp icon in a 48dp touch target
and matching start padding on the settings and about screens.

app/src/main/java/com/example/research/common/ui/AppBackButton.kt

@@ -0,0 +1,25 @@
+package com.example.research.common.ui
+
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import com.example.research.R
+
+@Composable
+fun AppBackButton(
+    onClick: () -> Unit,
+    modifier: Modifier = Modifier
+) {
+    IconButton(onClick = onClick, modifier = modifier.size(48.dp)) {
+        Icon(
+            painter = painterResource(R.drawable.ic_arrow_back),
+            contentDescription = stringResource(R.string.action_back),
+            modifier = Modifier.size(28.dp)
+        )
+    }
+}

app/src/main/java/com/example/research/ui/about/AboutScreen.kt

@@ -21,8 +21,6 @@ import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.AlertDialogDefaults
 import androidx.compose.material3.BasicAlertDialog
 import androidx.compose.material3.ExperimentalMaterial3Api
-import androidx.compose.material3.Icon
-import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Surface
@@ -46,13 +44,13 @@ import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.platform.LocalUriHandler
 import androidx.compose.ui.platform.LocalWindowInfo
 import androidx.compose.ui.platform.testTag
-import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.semantics.testTagsAsResourceId
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import com.example.research.R
+import com.example.research.common.ui.AppBackButton
 import com.example.research.common.ui.components.OutlinedChoiceButton
 import com.example.research.ui.theme.AppWindowInsets
 import kotlinx.coroutines.Dispatchers
@@ -94,12 +92,10 @@ fun AboutScreen(
             TopAppBar(
                 title = { Text(stringResource(R.string.about_app_title)) },
                 navigationIcon = {
-                    IconButton(onClick = onNavigateBack) {
-                        Icon(
-                            painter = painterResource(R.drawable.ic_arrow_back),
-                            contentDescription = stringResource(R.string.action_back)
+                    AppBackButton(
+                        onClick = onNavigateBack,
+                        modifier = Modifier.padding(start = 6.dp)
                     )
-                    }
                 },
                 colors = TopAppBarDefaults.topAppBarColors(
                     containerColor = MaterialTheme.colorScheme.surface

app/src/main/java/com/example/research/ui/settings/SettingsScreen.kt

@@ -21,7 +21,6 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
-import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.SnackbarHost
@@ -46,6 +45,7 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.repeatOnLifecycle
 import com.example.research.R
+import com.example.research.common.ui.AppBackButton
 import com.example.research.common.ui.appTestTag
 import com.example.research.common.ui.components.CollapsibleHeader
 import com.example.research.common.ui.components.SectionCard
@@ -126,13 +126,11 @@ fun SettingsScreen(
                 title = { Text(stringResource(R.string.settings_title)) },
                 navigationIcon = {
                     if (showBackButton) {
-                        IconButton(onClick = onNavigateBack) {
-                            Icon(
-                                painter = painterResource(R.drawable.ic_arrow_back),
-                                contentDescription = stringResource(R.string.action_back)
+                        AppBackButton(
+                            onClick = onNavigateBack,
+                            modifier = Modifier.padding(start = 6.dp)
                         )
                     }
-                    }
                 },
                 colors = TopAppBarDefaults.topAppBarColors(
                     containerColor = MaterialTheme.colorScheme.surface