feat: Add image viewer state management to disable swipe-back when photo is fullscreen

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

@@ -799,10 +799,14 @@ fun MainScreen(
             )
         }
 
+        // 🖼️ Image viewer state — disable swipe-back when photo is fullscreen
+        var isImageViewerOpen by remember { mutableStateOf(false) }
+
         SwipeBackContainer(
             isVisible = selectedUser != null,
             onBack = { selectedUser = null },
-            isDarkTheme = isDarkTheme
+            isDarkTheme = isDarkTheme,
+            swipeEnabled = !isImageViewerOpen
         ) {
             if (selectedUser != null) {
                 // Экран чата
@@ -821,7 +825,10 @@ fun MainScreen(
                             selectedUser = forwardUser
                         },
                         isDarkTheme = isDarkTheme,
-                        avatarRepository = avatarRepository
+                        avatarRepository = avatarRepository,
+                        onImageViewerChanged = { isOpen ->
+                            isImageViewerOpen = isOpen
+                        }
                 )
             }
         }

app/src/main/java/com/rosetta/messenger/ui/chats/ChatDetailScreen.kt

@@ -114,7 +114,8 @@ fun ChatDetailScreen(
         currentUserPrivateKey: String,
         totalUnreadFromOthers: Int = 0,
         isDarkTheme: Boolean,
-        avatarRepository: AvatarRepository? = null
+        avatarRepository: AvatarRepository? = null,
+        onImageViewerChanged: (Boolean) -> Unit = {}
 ) {
         val viewModel: ChatViewModel = viewModel(key = "chat_${user.publicKey}")
         val context = LocalContext.current
@@ -1813,6 +1814,7 @@ fun ChatDetailScreen(
                                                                                                 imageViewerInitialIndex = findImageIndex(allImages, attachmentId)
                                                                                                 imageViewerSourceBounds = bounds
                                                                                                 showImageViewer = true
+                                                                                                onImageViewerChanged(true)
                                                                                         }
                                                                                 )
                                                                         }
@@ -1886,6 +1888,7 @@ fun ChatDetailScreen(
                         onDismiss = {
                                 showImageViewer = false
                                 imageViewerSourceBounds = null
+                                onImageViewerChanged(false)
                         },
                         onClosingStart = {
                                 // Сразу сбрасываем status bar при начале закрытия (до анимации)