implemented a customizable chat background system with support for patterns, solid colors, and gallery images; added a dedicated settings page with live preview and adjustable blur/dim effects, updated the image cropper to support flexible aspect ratios for wallpapers, and integrated file cleanup logic during account logout.

lib/utils/app_paths.dart

@@ -0,0 +1,18 @@
+import 'dart:io';
+
+/// Holds filesystem paths that are resolved once during app startup so they can
+/// be read synchronously from widget `build()` methods (which cannot await the
+/// async `path_provider` lookups). [documentsDir] is populated in `main()`
+/// before `runApp`.
+class AppPaths {
+  /// Absolute path to the app's documents directory. Set exactly once during
+  /// startup; reading it before that completes throws (intentional — surfaces
+  /// an init-order bug instead of silently using an empty path).
+  static late final String documentsDir;
+
+  /// Persistent location of the user-chosen chat background image. Constant
+  /// filename, so replacing the image overwrites in place — callers must
+  /// `evict()` it from the image cache after writing.
+  static String get chatBackgroundImage =>
+      '$documentsDir${Platform.pathSeparator}chat_background.img';
+}