2.0: breakfast and snack meal types across the app

- MealType gains breakfast/snack (chronological order drives slot/row order).
- AppSettings.activeMealTypes: single source of truth for enabled meals, backed
  by new optional enabledMealTypesRaw with legacy mealWindows fallback —
  additive migration, keeps pre-2.0 installs and iCloud snapshots working.
  Legacy field kept coherent by the setter. time(for:) resolves per-meal event
  times (breakfast 8:00 / snack 17:00 defaults on old stores).
- Replaced the 5 duplicated mealWindows→[MealType] derivations (slot sync,
  default plan creation, week calendar, export view) with activeMealTypes.
- CalendarService: per-type event names and times.
- Export styles: per-type accent colors and gradients.
- Widget: generic meals list (N rows) instead of hardcoded lunch/dinner;
  compact families fall back to main meals when >2 are active.
- Settings: 4 meal toggles (min 1) replace the 3-option picker.
- Onboarding: meal step is now multi-select over the 4 types.
- iCloud sync: enabledMealTypesRaw synced (optional, pre-2.0 compatible).
- Localized breakfast/snack in all 6 languages.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BkanrydYtrme8wipTzWssG

MealMood/Resources/pt-BR.lproj/Localizable.strings

@@ -406,3 +406,7 @@
 "dish_ingredients_label" = "Ingredientes";
 "dish_ingredient_placeholder" = "ex.: 200 g de espaguete";
 "dish_ingredients_add" = "Adicionar ingrediente";
+
+// Meal types (2.0)
+"breakfast" = "Café da manhã";
+"snack" = "Lanche";