feat: Implement back button handling in ProfileScreen to navigate to chat list

app/src/main/java/com/rosetta/messenger/ui/settings/ProfileScreen.kt

@@ -6,6 +6,7 @@ import android.content.ClipboardManager
 import android.content.Context
 import android.net.Uri
 import android.util.Log
+import androidx.activity.compose.BackHandler
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.animation.*
@@ -344,6 +345,11 @@ fun ProfileScreen(
         hasChanges = editedName != accountName || editedUsername != accountUsername
     }
     
+    // Handle back button press - navigate to chat list instead of closing app
+    BackHandler {
+        onBack()
+    }
+
     Box(
         modifier = Modifier
             .fillMaxSize()
@@ -1067,22 +1073,12 @@ private fun TelegramBiometricItem(
 
         Spacer(modifier = Modifier.width(20.dp))
 
-        Column(modifier = Modifier.weight(1f)) {
-            Text(
-                text = "Biometric Authentication",
-                fontSize = 16.sp,
-                color = textColor
-            )
-            
-            if (isEnabled) {
-                Text(
-                    text = "Face ID / Touch ID",
-                    fontSize = 13.sp,
-                    color = textColor.copy(alpha = 0.5f),
-                    modifier = Modifier.padding(top = 2.dp)
-                )
-            }
-        }
+        Text(
+            text = "Biometric Authentication",
+            fontSize = 16.sp,
+            color = textColor,
+            modifier = Modifier.weight(1f)
+        )
         
         // iOS-style animated switch
         val animatedThumbOffset by animateFloatAsState(