[lcenavigationview-adoption] Suppress glass button chrome via .buttonStyle(.plain)

Cascades .buttonStyle(.plain) down from each LCENavigationView
instance instead of waiting on the LCEssentials package fix
(committed separately, unpublished: LC_Essentials commit 8b0f650) to
be released and this repo's Package.resolved bumped. Overrides
iOS 26's automatic Liquid Glass chrome on LCENavigationView's
internal nav buttons - including the invisible backfilled mirror
button on whichever side has no real action - without affecting any
button that already sets its own explicit style closer to itself.

PediFoods/Views/Main/CartView.swift

@@ -21,6 +21,7 @@ struct CartView: View {
         }
         .setTitle(text: Text("Meu Carrinho").font(AppTypography.heading1).foregroundStyle(AppColors.textPrimary))
         .setNavigationBarBackgroundColor(AppColors.backgroundLight)
+        .buttonStyle(.plain)
     }
 
     private var content: some View {