feat: add widget extension — small, medium, large

- KisaniCalWidget: 3 sizes sharing the app's design language
  Small: date badge + kisaniCAL. wordmark + task count
  Medium: badge + task list (3 items) + workout row
  Large: badge + full task list (6 items) + workout row

- WidgetDataStore (Shared/): lightweight Codable types for App Group
  UserDefaults cross-process data exchange

- WidgetBridge: TaskViewModel/WorkoutViewModel extensions that sync
  data into App Group and call WidgetCenter.reloadAllTimelines()

- ContentView: calls syncWidget() on appear and scene becoming active

- project.yml + entitlements updated; project regenerated via xcodegen

KisaniCal.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:">
+   </FileRef>
+</Workspace>