platos: segundo plato por comida (ensalada + salmon)

- MealSlot.secondaryDishId (opcional, aditivo CloudKit); se limpia al
  sustituir/quitar/vaciar/marcar comer fuera y viaja en swaps, copia de
  semana anterior, undo y snapshot KV de iCloud (retrocompatible)
- Picker de hueco lleno: toggle "anadir como segundo plato" + boton para
  quitarlo; HomeViewModel.assignSecondaryDish/removeSecondaryDish
- Se muestra "Plato + Segundo" en calendario, widget y export; la lista
  de la compra incluye los ingredientes del segundo; stats lo cuentan
- Evento analytics secondary_dish_added; strings en 6 idiomas

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013H6bXqGX1ygwib1Dm3n3UG

MealMood/Views/Home/HomeView.swift

@@ -570,7 +570,23 @@ struct HomeView: View {
                         DispatchQueue.main.asyncAfter(deadline: .now() + 0.15) {
                             attemptCreateDish()
                         }
-                    }
+                    },
+                    onPickSecondDish: { dish in
+                        guard let freshSlot = plan.slotList.first(where: { $0.id == slotId }) else {
+                            selectedFilledSlotId = nil
+                            return
+                        }
+                        viewModel.assignSecondaryDish(dish, to: freshSlot, plan: plan, settings: settings)
+                        selectedFilledSlotId = nil
+                    },
+                    onRemoveSecondDish: plan.slotList.first(where: { $0.id == slotId })?.secondaryDishId != nil ? {
+                        guard let freshSlot = plan.slotList.first(where: { $0.id == slotId }) else {
+                            selectedFilledSlotId = nil
+                            return
+                        }
+                        viewModel.removeSecondaryDish(from: freshSlot, plan: plan)
+                        selectedFilledSlotId = nil
+                    } : nil
                 )
             }
         }
@@ -673,9 +689,14 @@ struct HomeView: View {
         let onPickDish: (Dish) -> Void
         let onCreateDish: () -> Void
         var onEatingOut: (() -> Void)? = nil
+        /// Set for filled slots: taps add a companion dish instead of replacing
+        /// when the "second dish" mode is on.
+        var onPickSecondDish: ((Dish) -> Void)? = nil
+        var onRemoveSecondDish: (() -> Void)? = nil
 
         @Environment(\.dismiss) private var dismiss
         @State private var searchText: String = ""
+        @State private var asSecondDish: Bool = false
 
         private var filteredDishes: [Dish] {
             let trimmed = searchText.trimmingCharacters(in: .whitespacesAndNewlines)
@@ -720,9 +741,35 @@ struct HomeView: View {
                                 .listRowBackground(Color(hex: "#EEF8F5"))
                             }
 
+                            if onPickSecondDish != nil, searchText.isEmpty {
+                                Toggle(isOn: $asSecondDish) {
+                                    Label("home_pick_second_dish", systemImage: "plus.square.on.square")
+                                        .font(.mealMoodBody)
+                                        .foregroundColor(.mealMoodTextPrimary)
+                                }
+                                .tint(.mealMoodCoral)
+                                .listRowBackground(Color.mealMoodSurface)
+
+                                if let onRemoveSecondDish {
+                                    Button {
+                                        dismiss()
+                                        onRemoveSecondDish()
+                                    } label: {
+                                        Label("home_remove_second_dish", systemImage: "minus.square")
+                                            .font(.mealMoodBody)
+                                            .foregroundColor(.mealMoodError)
+                                    }
+                                    .listRowBackground(Color.mealMoodSurface)
+                                }
+                            }
+
                             ForEach(filteredDishes, id: \.id) { dish in
                                 Button {
-                                    onPickDish(dish)
+                                    if asSecondDish, let onPickSecondDish {
+                                        onPickSecondDish(dish)
+                                    } else {
+                                        onPickDish(dish)
+                                    }
                                     dismiss()
                                 } label: {
                                     VStack(alignment: .leading, spacing: 6) {