feat: Enhance chat UI with group invite handling and new download indicator

- Added support for standalone group invites in MessageBubble component.
- Improved bubble padding and width handling for group invites.
- Refactored MessageBubble to streamline background and border logic.
- Introduced AnimatedDownloadIndicator for a more engaging download experience.
- Created ThemeWallpapers data structure to manage chat wallpapers.
- Implemented WallpaperSelectorRow and WallpaperSelectorItem for theme customization.
- Updated ThemeScreen to allow wallpaper selection and preview.
- Added new drawable resources for download and search icons.

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

@@ -676,6 +676,7 @@ fun MainScreen(
             prefsManager
                     .backgroundBlurColorIdForAccount(accountPublicKey)
                     .collectAsState(initial = "avatar")
+    val chatWallpaperId by prefsManager.chatWallpaperId.collectAsState(initial = "")
     val pinnedChats by prefsManager.pinnedChats.collectAsState(initial = emptySet())
 
     // AvatarRepository для работы с аватарами
@@ -899,8 +900,12 @@ fun MainScreen(
             ThemeScreen(
                     isDarkTheme = isDarkTheme,
                     currentThemeMode = themeMode,
+                    currentWallpaperId = chatWallpaperId,
                     onBack = { navStack = navStack.filterNot { it is Screen.Theme } },
-                    onThemeModeChange = onThemeModeChange
+                    onThemeModeChange = onThemeModeChange,
+                    onWallpaperChange = { wallpaperId ->
+                        mainScreenScope.launch { prefsManager.setChatWallpaperId(wallpaperId) }
+                    }
             )
         }
 
@@ -989,6 +994,7 @@ fun MainScreen(
                                     } + Screen.ChatDetail(forwardUser)
                         },
                         isDarkTheme = isDarkTheme,
+                        chatWallpaperId = chatWallpaperId,
                         avatarRepository = avatarRepository,
                         onImageViewerChanged = { isLocked -> isChatSwipeLocked = isLocked }
                 )