feat: Add appearance customization screen with background blur options

- Introduced `BackgroundBlurOption` data class and `BackgroundBlurPresets` object for managing background blur options.
- Created `AppearanceScreen` composable for selecting background colors and gradients, including a live preview of the selected option.
- Updated `OtherProfileScreen` and `ProfileScreen` to accept and utilize `backgroundBlurColorId` for consistent background blur across profiles.
- Enhanced `CollapsingOtherProfileHeader` and `CollapsingProfileHeader` to apply selected background blur options.

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

@@ -542,11 +542,16 @@ fun MainScreen(
     var showLogsScreen by remember { mutableStateOf(false) }
     var showCrashLogsScreen by remember { mutableStateOf(false) }
     var showBiometricScreen by remember { mutableStateOf(false) }
+    var showAppearanceScreen by remember { mutableStateOf(false) }
 
     // ProfileViewModel для логов
     val profileViewModel: com.rosetta.messenger.ui.settings.ProfileViewModel = androidx.lifecycle.viewmodel.compose.viewModel()
     val profileState by profileViewModel.state.collectAsState()
     
+    // Appearance: background blur color preference
+    val prefsManager = remember { com.rosetta.messenger.data.PreferencesManager(context) }
+    val backgroundBlurColorId by prefsManager.backgroundBlurColorId.collectAsState(initial = "avatar")
+    
     // AvatarRepository для работы с аватарами
     val avatarRepository = remember(accountPublicKey) {
         if (accountPublicKey.isNotBlank() && accountPublicKey != "04c266b98ae5") {
@@ -608,10 +613,61 @@ fun MainScreen(
                     // TODO: Show new chat screen
                 },
                 onUserSelect = { selectedChatUser -> selectedUser = selectedChatUser },
+                backgroundBlurColorId = backgroundBlurColorId,
                 avatarRepository = avatarRepository,
                 onLogout = onLogout
             )
 
+        // ═══════════════════════════════════════════════════════════
+        // Profile Screen — MUST be before sub-screens so it stays
+        // visible beneath them during swipe-back animation
+        // ═══════════════════════════════════════════════════════════
+        SwipeBackContainer(
+            isVisible = showProfileScreen,
+            onBack = { showProfileScreen = false },
+            isDarkTheme = isDarkTheme
+        ) {
+            // Экран профиля
+            ProfileScreen(
+                    isDarkTheme = isDarkTheme,
+                    accountName = accountName,
+                    accountUsername = accountUsername,
+                    accountPublicKey = accountPublicKey,
+                    accountPrivateKeyHash = privateKeyHash,
+                    onBack = { showProfileScreen = false },
+                    onSaveProfile = { name, username ->
+                        accountName = name
+                        accountUsername = username
+                        mainScreenScope.launch {
+                            onAccountInfoUpdated()
+                        }
+                    },
+                    onLogout = onLogout,
+                    onNavigateToTheme = {
+                        showThemeScreen = true
+                    },
+                    onNavigateToAppearance = {
+                        showAppearanceScreen = true
+                    },
+                    onNavigateToSafety = {
+                        showSafetyScreen = true
+                    },
+                    onNavigateToLogs = {
+                        showLogsScreen = true
+                    },
+                    onNavigateToCrashLogs = {
+                        showCrashLogsScreen = true
+                    },
+                    onNavigateToBiometric = {
+                        showBiometricScreen = true
+                    },
+                    viewModel = profileViewModel,
+                    avatarRepository = avatarRepository,
+                    dialogDao = RosettaDatabase.getDatabase(context).dialogDao(),
+                    backgroundBlurColorId = backgroundBlurColorId
+            )
+        }
+
         // Other screens with swipe back
         SwipeBackContainer(
             isVisible = showBackupScreen,
@@ -705,6 +761,33 @@ fun MainScreen(
             )
         }
 
+        SwipeBackContainer(
+            isVisible = showAppearanceScreen,
+            onBack = {
+                showAppearanceScreen = false
+                showProfileScreen = true
+            },
+            isDarkTheme = isDarkTheme
+        ) {
+            com.rosetta.messenger.ui.settings.AppearanceScreen(
+                isDarkTheme = isDarkTheme,
+                currentBlurColorId = backgroundBlurColorId,
+                onBack = {
+                    showAppearanceScreen = false
+                    showProfileScreen = true
+                },
+                onBlurColorChange = { newId ->
+                    mainScreenScope.launch {
+                        prefsManager.setBackgroundBlurColorId(newId)
+                    }
+                },
+                onToggleTheme = onToggleTheme,
+                accountPublicKey = accountPublicKey,
+                accountName = accountName,
+                avatarRepository = avatarRepository
+            )
+        }
+
         SwipeBackContainer(
             isVisible = showUpdatesScreen,
             onBack = { showUpdatesScreen = false },
@@ -762,58 +845,6 @@ fun MainScreen(
             )
         }
 
-        SwipeBackContainer(
-            isVisible = showProfileScreen,
-            onBack = { showProfileScreen = false },
-            isDarkTheme = isDarkTheme
-        ) {
-            // Экран профиля
-            ProfileScreen(
-                    isDarkTheme = isDarkTheme,
-                    accountName = accountName,
-                    accountUsername = accountUsername,
-                    accountPublicKey = accountPublicKey,
-                    accountPrivateKeyHash = privateKeyHash,
-                    onBack = { showProfileScreen = false },
-                    onSaveProfile = { name, username ->
-                        // Following desktop version pattern:
-                        // 1. Server confirms save (handled in ProfileViewModel)
-                        // 2. Local DB updated (handled in ProfileScreen LaunchedEffect)
-                        // 3. This callback updates UI state immediately
-                        accountName = name
-                        accountUsername = username
-                        // Reload account list so auth screen shows updated name
-                        mainScreenScope.launch {
-                            onAccountInfoUpdated()
-                        }
-                    },
-                    onLogout = onLogout,
-                    onNavigateToTheme = {
-                        showProfileScreen = false
-                        showThemeScreen = true
-                    },
-                    onNavigateToSafety = {
-                        showProfileScreen = false
-                        showSafetyScreen = true
-                    },
-                    onNavigateToLogs = {
-                        showProfileScreen = false
-                        showLogsScreen = true
-                    },
-                    onNavigateToCrashLogs = {
-                        showProfileScreen = false
-                        showCrashLogsScreen = true
-                    },
-                    onNavigateToBiometric = {
-                        showProfileScreen = false
-                        showBiometricScreen = true
-                    },
-                    viewModel = profileViewModel,
-                    avatarRepository = avatarRepository,
-                    dialogDao = RosettaDatabase.getDatabase(context).dialogDao()
-            )
-        }
-
         SwipeBackContainer(
             isVisible = showLogsScreen,
             onBack = {
@@ -867,7 +898,8 @@ fun MainScreen(
                         showOtherProfileScreen = false
                         selectedOtherUser = null
                     },
-                    avatarRepository = avatarRepository
+                    avatarRepository = avatarRepository,
+                    backgroundBlurColorId = backgroundBlurColorId
                 )
             }
         }