overhauled feedback dialog UI, implemented async action buttons for submission and image picking, and added a custom image preview widget

lib/widget/file_pick.dart

@@ -9,6 +9,9 @@ class FilePick {
     return pickedImages.isNotEmpty ? pickedImages : null;
   }
 
+  static Future<XFile?> singleGalleryPick() =>
+      _picker.pickImage(source: ImageSource.gallery);
+
   static Future<XFile?> cameraPick() =>
       _picker.pickImage(source: ImageSource.camera);