feat: Add total unread count from other chats for back-chevron badge in MainScreen

app/src/main/java/com/rosetta/messenger/MainActivity.kt

@@ -971,6 +971,17 @@ fun MainScreen(
         // 🔒 Lock swipe-back while chat overlays are open (image viewer/editor/media picker/camera).
         var isChatSwipeLocked by remember { mutableStateOf(false) }
 
+        // 🔴 Badge: total unread from OTHER chats (excluding current) for back-chevron badge
+        val totalUnreadFromOthers by remember(accountPublicKey, selectedUser?.publicKey) {
+            val db = RosettaDatabase.getDatabase(context)
+            val opponentKey = selectedUser?.publicKey ?: ""
+            if (accountPublicKey.isNotBlank() && opponentKey.isNotBlank()) {
+                db.dialogDao().getTotalUnreadCountExcludingFlow(accountPublicKey, opponentKey)
+            } else {
+                kotlinx.coroutines.flow.flowOf(0)
+            }
+        }.collectAsState(initial = 0)
+
         SwipeBackContainer(
                 isVisible = selectedUser != null,
                 onBack = { popChatAndChildren() },
@@ -984,6 +995,7 @@ fun MainScreen(
                         currentUserPublicKey = accountPublicKey,
                         currentUserPrivateKey = accountPrivateKey,
                         currentUserName = accountName,
+                        totalUnreadFromOthers = totalUnreadFromOthers,
                         onBack = { popChatAndChildren() },
                         onUserProfileClick = { user ->
                             if (user.publicKey == accountPublicKey) {