feat: My Tasks widget, event countdown redesign, completed section

- My Tasks widget: today's tasks with interactive check-off (ToggleTaskIntent)
  and a "+" that opens the app's add-task sheet; writes preserve all task
  fields and sync via the App Group.
- Event Countdown: AZURE/AWS-style header (accent name + countdown label +
  percent); tap the label to cycle days → weeks → time remaining.
- Today: collapsible "Completed" archive section below Upcoming.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

KisaniCal/ContentView.swift

@@ -68,6 +68,14 @@ struct ContentView: View {
 
     private var isIPad: Bool { UIDevice.current.userInterfaceIdiom == .pad }
 
+    /// Picks up the "+" tapped on the My Tasks widget and opens the add-task sheet.
+    private func consumeWidgetAddTask() {
+        guard UserDefaults.kisani.bool(forKey: "kisani.widget.openAddTask") else { return }
+        UserDefaults.kisani.removeObject(forKey: "kisani.widget.openAddTask")
+        selectedTab = 0
+        showQuickAddTask = true
+    }
+
     var body: some View {
         Group {
             if isIPad {
@@ -89,6 +97,7 @@ struct ContentView: View {
             CloudSyncManager.shared.backupSettings()
             HealthKitManager.shared.bootstrap()
             NotificationManager.shared.reschedule(workoutVM: workoutVM, taskVM: taskVM)
+            consumeWidgetAddTask()
             // Pull workouts from Health, then reschedule so a detected workout updates reminders.
             Task {
                 await workoutVM.syncFromHealthKit()
@@ -98,6 +107,7 @@ struct ContentView: View {
         .onChange(of: scenePhase) { phase in
             if phase == .active {
                 taskVM.reload()
+                consumeWidgetAddTask()
                 workoutVM.checkPendingHealthConfirm()
                 CloudSyncManager.shared.backupSettings()
                 NotificationManager.shared.reschedule(workoutVM: workoutVM, taskVM: taskVM)