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/storage/chat_background_settings.dart

@@ -0,0 +1,46 @@
+import 'package:json_annotation/json_annotation.dart';
+
+part 'chat_background_settings.g.dart';
+
+/// Source of the chat background.
+/// * [pattern] — the bundled tiled asset (legacy default, dark-mode inverted)
+/// * [image] — a user-picked image stored at [AppPaths.chatBackgroundImage]
+/// * [color] — a single solid colour ([ChatBackgroundSettings.colorValue])
+/// * [none] — plain theme surface colour
+enum ChatBackgroundType { pattern, image, color, none }
+
+/// How [ChatBackgroundType.pattern]/[ChatBackgroundType.image] fill the area.
+enum ChatBackgroundFit { cover, tile, center }
+
+@JsonSerializable()
+class ChatBackgroundSettings {
+  ChatBackgroundType type;
+  ChatBackgroundFit fit;
+
+  /// ARGB colour for [ChatBackgroundType.color]; null until the user picks one.
+  int? colorValue;
+
+  /// Monotonically increasing cache-buster. The image lives under a constant
+  /// filename, so Flutter's [ImageCache] can't tell a replacement apart — this
+  /// counter drives a [ValueKey] that forces a fresh subtree after a swap.
+  int imageVersion;
+
+  /// Strength of the black dim overlay drawn above the background (0..1).
+  double dim;
+
+  /// Gaussian blur sigma applied to the pattern/image layer (0..~25).
+  double blur;
+
+  ChatBackgroundSettings({
+    required this.type,
+    required this.fit,
+    required this.colorValue,
+    required this.imageVersion,
+    required this.dim,
+    required this.blur,
+  });
+
+  factory ChatBackgroundSettings.fromJson(Map<String, dynamic> json) =>
+      _$ChatBackgroundSettingsFromJson(json);
+  Map<String, dynamic> toJson() => _$ChatBackgroundSettingsToJson(this);
+}