Ingredient unit

When creating an ingredient, let user choose unit (gram, kg, per piece, etc...). Use this unit in the create meal tab when user selects the ingredients

Locate the ingredient-creation entry point and the create meal tab, then trace how ingredient data is stored and read when an ingredient is selected. Add the unit choices described in the issue and verify that the selected unit is available and used in the create meal flow.

Written by the indexing model from the issue text.