fix: 4335 - "check" icon for "done" details - instead of "edit"

Impacted files:
* `add_new_product_helper.dart`: added a specific trailing icon in some cases
* `smooth_large_button_with_icon.dart`: fixed color bug

packages/smooth_app/lib/generic_lib/buttons/smooth_large_button_with_icon.dart

@@ -36,7 +36,7 @@ class SmoothLargeButtonWithIcon extends StatelessWidget {
     final ThemeData themeData = Theme.of(context);
     TextStyle style = textStyle ?? themeData.textTheme.bodyMedium!;
 
-    if (style.color == null) {
+    if (foregroundColor != null) {
       style = style.copyWith(color: _getForegroundColor(themeData));
     }
 

packages/smooth_app/lib/pages/product/add_new_product_helper.dart

@@ -72,12 +72,14 @@ class AddNewProductButton extends StatelessWidget {
     this.iconData,
     this.onPressed, {
     required this.done,
+    this.trailingIconData,
   });
 
   final String label;
   final IconData iconData;
   final VoidCallback? onPressed;
   final bool done;
+  final IconData? trailingIconData;
 
   static const IconData doneIconData = Icons.check;
   static const IconData todoIconData = Icons.add;
@@ -95,7 +97,7 @@ class AddNewProductButton extends StatelessWidget {
         text: label,
         icon: iconData,
         onPressed: onPressed,
-        trailing: Icons.edit,
+        trailing: trailingIconData ?? Icons.edit,
         backgroundColor: onPressed == null
             ? (dark ? darkGrey : lightGrey)
             : done
@@ -144,6 +146,7 @@ class AddNewProductEditorButton extends StatelessWidget {
                 isLoggedInMandatory: isLoggedInMandatory,
               ),
       done: done,
+      trailingIconData: done ? AddNewProductButton.doneIconData : null,
     );
   }
 }