feat: per-ingredient category selection for shopping list transfer (closes #33)

When adding ingredients in the meal editor, each ingredient now has a
category dropdown. Categories are stored on the ingredient and applied
automatically when transferring to the shopping list, so items appear
pre-grouped by category without manual re-sorting.

public/locales/fr.json

@@ -226,6 +226,8 @@
     "addIngredient": "Ajouter un ingrédient",
     "ingredientNamePlaceholder": "Ingrédient",
     "ingredientQtyPlaceholder": "Quantité",
+    "ingredientCategoryLabel": "Catégorie",
+    "ingredientCategoryDefault": "Divers",
     "removeIngredient": "Supprimer l'ingrédient",
     "transferLabel": "Transférer les ingrédients vers la liste de courses",
     "transferNow": "Transférer maintenant",
@@ -596,4 +598,4 @@
     "unitMonth": "mois",
     "unitMonths": "mois"
   }
-}
+}