fix: #31 — changing quantity auto-recalculates macros in draft card

Captures base per-unit values (calories/protein/carbs/fat/sugar/fiber
divided by original quantity) when draft first appears. When quantity
changes, recalculateMacros() multiplies base values by new quantity.

Example: AI drafts "1 medium banana" at 105 cal. User changes
quantity to 2.0 → calories becomes 210, protein doubles, etc.

Values round to integers for calories, 1 decimal for macros.

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

ios/Platform/Platform/Features/Assistant/EditableDraftCard.swift

@@ -3,6 +3,13 @@ import SwiftUI
 struct EditableDraftCard: View {
     @Bindable var vm: AssistantViewModel
     @State private var isEditing = false
+    // Base values per 1.0 quantity — set once when draft appears
+    @State private var baseCalories: Double?
+    @State private var baseProtein: Double?
+    @State private var baseCarbs: Double?
+    @State private var baseFat: Double?
+    @State private var baseSugar: Double?
+    @State private var baseFiber: Double?
 
     private var draft: FitnessDraft? { vm.currentDraft }
 
@@ -135,8 +142,34 @@ struct EditableDraftCard: View {
             .clipShape(RoundedRectangle(cornerRadius: 14))
             .shadow(color: .black.opacity(0.06), radius: 6, y: 2)
             .padding(.horizontal, 12)
+            .onAppear {
+                // Capture base per-unit values on first appearance
+                if baseCalories == nil, let d = vm.currentDraft {
+                    let q = max(d.quantity, 0.01)
+                    baseCalories = d.calories / q
+                    baseProtein = d.protein / q
+                    baseCarbs = d.carbs / q
+                    baseFat = d.fat / q
+                    baseSugar = d.sugar / q
+                    baseFiber = d.fiber / q
                 }
             }
+        }
+    }
+
+    /// Recalculate macros from base values when quantity changes
+    private func recalculateMacros() {
+        guard let bc = baseCalories, let bp = baseProtein,
+              let bca = baseCarbs, let bf = baseFat,
+              let bs = baseSugar, let bfi = baseFiber else { return }
+        let q = vm.currentDraft?.quantity ?? 1.0
+        vm.currentDraft?.calories = (bc * q).rounded()
+        vm.currentDraft?.protein = (bp * q * 10).rounded() / 10
+        vm.currentDraft?.carbs = (bca * q * 10).rounded() / 10
+        vm.currentDraft?.fat = (bf * q * 10).rounded() / 10
+        vm.currentDraft?.sugar = (bs * q * 10).rounded() / 10
+        vm.currentDraft?.fiber = (bfi * q * 10).rounded() / 10
+    }
 
     // MARK: - Editable macro cell
 
@@ -196,7 +229,10 @@ struct EditableDraftCard: View {
     private var quantityBinding: Binding<String> {
         Binding(
             get: { String(format: "%.1f", vm.currentDraft?.quantity ?? 1) },
-            set: { vm.currentDraft?.quantity = Double($0) ?? 1 }
+            set: {
+                vm.currentDraft?.quantity = Double($0) ?? 1
+                recalculateMacros()
+            }
         )
     }
 }