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>

KisaniCalWidgets/KisaniCalWidgets.swift

@@ -106,6 +106,7 @@ struct LockScreenCircularWidget: Widget {
 struct KisaniWidgetBundle: WidgetBundle {
     var body: some Widget {
         EventCountdownWidget()
+        MyTasksWidget()
         DayProgressWidget()
         TasksCompleteWidget()
         LockScreenWidget()