feat: calorie ring widget — home screen + lock screen

Widget displays:
- systemSmall: calorie ring + "X left" text
- systemMedium: ring + "Calories" / "X of Y" / "X remaining"
- accessoryCircular: gauge ring for lock screen
- accessoryInline: "🔥 845 / 2000 cal" text for lock screen
- accessoryRectangular: linear gauge + calorie count

Data flow: main app writes totalCalories + calorieGoal to
UserDefaults on each loadTodayData(), then calls
WidgetCenter.shared.reloadAllTimelines(). Widget reads on
15-minute refresh cycle.

Note: currently uses standard UserDefaults (same app container).
For production, migrate to App Group UserDefaults so widget
process can read the data. Requires Xcode App Group setup.

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

ios/Platform/PlatformWidget/PlatformWidget.swift

@@ -1,62 +1,220 @@
 import WidgetKit
 import SwiftUI
 
-struct Provider: TimelineProvider {
-    func placeholder(in context: Context) -> SimpleEntry {
-        SimpleEntry(date: Date())
+// MARK: - Shared data key (main app writes, widget reads)
+// Uses standard UserDefaults for now. Migrate to App Group
+// UserDefaults when App Group is configured in Xcode.
+
+private let caloriesKey = "widget_totalCalories"
+private let goalKey = "widget_calorieGoal"
+
+// MARK: - Timeline
+
+struct CalorieEntry: TimelineEntry {
+    let date: Date
+    let totalCalories: Double
+    let calorieGoal: Double
+
+    var progress: Double {
+        guard calorieGoal > 0 else { return 0 }
+        return min(max(totalCalories / calorieGoal, 0), 1.0)
     }
 
-    func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> Void) {
-        let entry = SimpleEntry(date: Date())
-        completion(entry)
+    var remaining: Double {
+        max(calorieGoal - totalCalories, 0)
+    }
+}
+
+struct CalorieProvider: TimelineProvider {
+    func placeholder(in context: Context) -> CalorieEntry {
+        CalorieEntry(date: .now, totalCalories: 845, calorieGoal: 2000)
     }
 
-    func getTimeline(in context: Context, completion: @escaping (Timeline<SimpleEntry>) -> Void) {
-        var entries: [SimpleEntry] = []
-        let currentDate = Date()
-        for hourOffset in 0 ..< 5 {
-            let entryDate = Calendar.current.date(byAdding: .hour, value: hourOffset, to: currentDate)!
-            let entry = SimpleEntry(date: entryDate)
-            entries.append(entry)
-        }
-        let timeline = Timeline(entries: entries, policy: .atEnd)
+    func getSnapshot(in context: Context, completion: @escaping (CalorieEntry) -> Void) {
+        completion(readEntry())
+    }
+
+    func getTimeline(in context: Context, completion: @escaping (Timeline<CalorieEntry>) -> Void) {
+        let entry = readEntry()
+        // Refresh every 15 minutes
+        let nextUpdate = Calendar.current.date(byAdding: .minute, value: 15, to: entry.date)!
+        let timeline = Timeline(entries: [entry], policy: .after(nextUpdate))
         completion(timeline)
     }
+
+    private func readEntry() -> CalorieEntry {
+        let defaults = UserDefaults.standard
+        let calories = defaults.double(forKey: caloriesKey)
+        let goal = defaults.double(forKey: goalKey)
+        return CalorieEntry(
+            date: .now,
+            totalCalories: calories,
+            calorieGoal: goal > 0 ? goal : 2000
+        )
+    }
 }
 
-struct SimpleEntry: TimelineEntry {
-    let date: Date
-}
+// MARK: - Widget Views
 
-struct PlatformWidgetEntryView: View {
-    var entry: Provider.Entry
+struct CalorieRingView: View {
+    let entry: CalorieEntry
+    let size: CGFloat
+    let lineWidth: CGFloat
+
+    private let ringColor = Color(red: 0.020, green: 0.588, blue: 0.412) // emerald
 
     var body: some View {
-        VStack {
-            Text("Platform")
-                .font(.headline)
-            Text(entry.date, style: .time)
-                .font(.caption)
+        ZStack {
+            // Background ring
+            Circle()
+                .stroke(ringColor.opacity(0.2), lineWidth: lineWidth)
+
+            // Progress ring
+            Circle()
+                .trim(from: 0, to: entry.progress)
+                .stroke(ringColor, style: StrokeStyle(lineWidth: lineWidth, lineCap: .round))
+                .rotationEffect(.degrees(-90))
+
+            // Center text
+            VStack(spacing: 1) {
+                Text("\(Int(entry.totalCalories))")
+                    .font(.system(size: size * 0.22, weight: .bold, design: .rounded))
+                    .foregroundStyle(.primary)
+                Text("/ \(Int(entry.calorieGoal))")
+                    .font(.system(size: size * 0.1, weight: .medium, design: .rounded))
+                    .foregroundStyle(.secondary)
+            }
+        }
+        .frame(width: size, height: size)
+    }
+}
+
+struct SmallWidgetView: View {
+    let entry: CalorieEntry
+
+    var body: some View {
+        VStack(spacing: 8) {
+            CalorieRingView(entry: entry, size: 90, lineWidth: 8)
+
+            Text("\(Int(entry.remaining)) left")
+                .font(.caption2.weight(.medium))
+                .foregroundStyle(.secondary)
+        }
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
+    }
+}
+
+struct MediumWidgetView: View {
+    let entry: CalorieEntry
+
+    var body: some View {
+        HStack(spacing: 20) {
+            CalorieRingView(entry: entry, size: 100, lineWidth: 9)
+
+            VStack(alignment: .leading, spacing: 6) {
+                Text("Calories")
+                    .font(.headline)
+                    .foregroundStyle(.primary)
+
+                Text("\(Int(entry.totalCalories)) of \(Int(entry.calorieGoal))")
+                    .font(.subheadline)
+                    .foregroundStyle(.secondary)
+
+                Text("\(Int(entry.remaining)) remaining")
+                    .font(.caption)
+                    .foregroundStyle(.tertiary)
+            }
+        }
+        .frame(maxWidth: .infinity, maxHeight: .infinity)
+    }
+}
+
+// Lock screen widgets
+struct CircularWidgetView: View {
+    let entry: CalorieEntry
+
+    var body: some View {
+        Gauge(value: entry.progress) {
+            Text("\(Int(entry.totalCalories))")
+                .font(.system(size: 12, weight: .bold, design: .rounded))
+        }
+        .gaugeStyle(.accessoryCircular)
+        .tint(Color(red: 0.020, green: 0.588, blue: 0.412))
+    }
+}
+
+struct InlineWidgetView: View {
+    let entry: CalorieEntry
+
+    var body: some View {
+        Text("🔥 \(Int(entry.totalCalories)) / \(Int(entry.calorieGoal)) cal")
+    }
+}
+
+struct RectangularWidgetView: View {
+    let entry: CalorieEntry
+
+    var body: some View {
+        HStack(spacing: 8) {
+            Gauge(value: entry.progress) {
+                EmptyView()
+            }
+            .gaugeStyle(.accessoryLinear)
+            .tint(Color(red: 0.020, green: 0.588, blue: 0.412))
+
+            Text("\(Int(entry.totalCalories)) cal")
+                .font(.system(size: 13, weight: .bold, design: .rounded))
         }
     }
 }
 
+// MARK: - Widget Configuration
+
 struct PlatformWidget: Widget {
     let kind: String = "PlatformWidget"
 
     var body: some WidgetConfiguration {
-        StaticConfiguration(kind: kind, provider: Provider()) { entry in
+        StaticConfiguration(kind: kind, provider: CalorieProvider()) { entry in
             PlatformWidgetEntryView(entry: entry)
                 .containerBackground(.fill.tertiary, for: .widget)
         }
-        .configurationDisplayName("Platform")
-        .description("Platform widget.")
-        .supportedFamilies([.systemSmall, .systemMedium])
+        .configurationDisplayName("Calories")
+        .description("Today's calorie progress ring.")
+        .supportedFamilies([
+            .systemSmall,
+            .systemMedium,
+            .accessoryCircular,
+            .accessoryInline,
+            .accessoryRectangular,
+        ])
+    }
+}
+
+// Use @ViewBuilder to pick the right view per family
+struct PlatformWidgetEntryView: View {
+    @Environment(\.widgetFamily) var family
+    let entry: CalorieEntry
+
+    var body: some View {
+        switch family {
+        case .systemSmall:
+            SmallWidgetView(entry: entry)
+        case .systemMedium:
+            MediumWidgetView(entry: entry)
+        case .accessoryCircular:
+            CircularWidgetView(entry: entry)
+        case .accessoryInline:
+            InlineWidgetView(entry: entry)
+        case .accessoryRectangular:
+            RectangularWidgetView(entry: entry)
+        default:
+            SmallWidgetView(entry: entry)
+        }
     }
 }
 
 #Preview(as: .systemSmall) {
     PlatformWidget()
 } timeline: {
-    SimpleEntry(date: .now)
+    CalorieEntry(date: .now, totalCalories: 845, calorieGoal: 2000)
 }