✨ Background image & appearance settings

lib/widgets/navigation/app_background.dart

@@ -1,4 +1,8 @@
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:path_provider/path_provider.dart';
 
 class AppBackground extends StatelessWidget {
   final Widget child;
@@ -6,6 +10,39 @@ class AppBackground extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return ScaffoldMessenger(child: child);
+    return ScaffoldMessenger(
+      child: FutureBuilder(
+        future:
+            kIsWeb ? Future.value(null) : getApplicationDocumentsDirectory(),
+        builder: (context, snapshot) {
+          if (snapshot.hasData) {
+            final path = '${snapshot.data!.path}/app_background_image';
+            final file = File(path);
+            if (file.existsSync()) {
+              return Container(
+                color: Theme.of(context).colorScheme.surface,
+                child: Container(
+                  decoration: BoxDecoration(
+                    backgroundBlendMode: BlendMode.darken,
+                    color: Theme.of(context).colorScheme.surface,
+                    image: DecorationImage(
+                      opacity: 0.2,
+                      image: FileImage(file),
+                      fit: BoxFit.cover,
+                    ),
+                  ),
+                  child: child,
+                ),
+              );
+            }
+          }
+
+          return Material(
+            color: Theme.of(context).colorScheme.surface,
+            child: child,
+          );
+        },
+      ),
+    );
   }
 }