feat: canvas-confetti style celebration + Quick Add callback

Confetti:
- 60 particles in 3 layered bursts (like canvas-confetti)
- Circles, rectangles, stars in 12 vibrant colors
- Physics: drift, spin, gravity, fade, scale
- Checkmark + 'Added!' text with spring animation
- Haptic feedback

Quick Add:
- FoodSearchView + AddFoodSheet now have onFoodAdded callback
- After adding from Quick Add: dismiss → fitness tab → confetti

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ios/Platform/Platform/Features/Fitness/Views/AddFoodSheet.swift

@@ -3,6 +3,7 @@ import SwiftUI
 struct AddFoodSheet: View {
     @Environment(\.dismiss) private var dismiss
     let food: Food
+    var onFoodAdded: (() -> Void)?
 
     @State private var quantity: Double = 1.0
     @State private var selectedMeal: MealType = .snack
@@ -234,6 +235,7 @@ struct AddFoodSheet: View {
                 )
                 _ = try await FitnessRepository.shared.createEntry(request)
                 dismiss()
+                onFoodAdded?()
             } catch {
                 self.error = error.localizedDescription
             }

ios/Platform/Platform/Features/Fitness/Views/FoodSearchView.swift

@@ -2,6 +2,7 @@ import SwiftUI
 
 struct FoodSearchView: View {
     var isSheet: Bool = false
+    var onFoodAdded: (() -> Void)?
     @State private var vm = FoodSearchViewModel()
     @State private var selectedFood: Food?
 
@@ -48,7 +49,7 @@ struct FoodSearchView: View {
             vm.search()
         }
         .sheet(item: $selectedFood) { food in
-            AddFoodSheet(food: food)
+            AddFoodSheet(food: food, onFoodAdded: onFoodAdded)
         }
     }