reglas: plato fijo por dia y comida (ej. tortilla los viernes de cena)

- Dish.fixedDayOfWeek/fixedMealType (opcionales, aditivos para CloudKit)
- Toggle + pickers de dia/comida en el formulario de plato
- AutocompleteEngine: pre-pasada que asigna los platos fijos a su hueco
  antes del bucle MRV, de modo que cuentan para el resto de reglas
- Evento analytics dish_fixed_slot_set; strings en 6 idiomas

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

MealMood/Services/AutocompleteEngine.swift

@@ -33,6 +33,18 @@ struct AutocompleteEngine {
         var unfilledCount = 0
         var pendingSlots = emptySlots.filter { !$0.isEatingOut }
 
+        // Fixed-slot rules win outright: a dish pinned to a weekday+meal fills
+        // that slot before any scoring. Runs before the MRV loop so the pinned
+        // dish also counts against no-repeat/tag rules for the rest of the week.
+        for slot in pendingSlots {
+            guard let fixed = allDishes.first(where: {
+                $0.fixedDayOfWeek == slot.dayOfWeek && $0.fixedMealType == slot.mealType
+            }) else { continue }
+            slot.dishId = fixed.id
+            filledSlots.append((slotId: slot.id, dishId: fixed.id))
+        }
+        pendingSlots.removeAll { $0.dishId != nil }
+
         // MRV: at each step pick the slot with fewest valid candidates first.
         // Assignments update currentPlan.slotList in-place, so subsequent candidate
         // counts automatically reflect the growing set of committed dishes.