Add vegan and vegetarian fields and filters to the ingredient

[rolandgeider]

Related Issue(s)

Flutter part of wger-project/wger#2217

[mubashardev]

Overall
Great PR! The implementation for filtering by dietary preferences is clean, localization is handled well, and the added test coverage in ingredient_typeahead_test.dart is excellent.

I've left a few minor non-blocking suggestions below for your consideration. Nice work!

Minor Suggestions (Non-blocking):

1. State Management Clarity (lib/widgets/nutrition/widgets.dart):
   In the StatefulBuilder's onChanged callbacks, the setState shadowing is functional but could be slightly clearer for readability:

onChanged: (val) {
  this.setState(() { 
     _isVegan = val; // Clearly updates the parent Widget state
  });
  setState(() {}); // Signals StatefulBuilder dialog to rebuild its UI
},

2. Query Parameters (lib/providers/nutrition.dart):
   Currently passing 'True' (capitalized) for the query parameter. While Django REST Framework typically handles this fine, standard web serialization generally favors lowercase ('true') for booleans across the wire.

[rolandgeider]

yes you are right, I've clean up a bit the code