Add onboarding UI tests and improve app data management

- Add Suite0_OnboardingTests with fresh install and login test flows
- Add accessibility identifiers to onboarding views for UI testing
- Remove deprecated DataCache in favor of unified DataManager
- Update API layer to support public upgrade-triggers endpoint
- Improve onboarding first task view with better date handling
- Update various views with accessibility identifiers for testing
- Fix subscription feature comparison view layout
- Update document detail view improvements

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

iosApp/TaskWidgetExample.swift

@@ -15,7 +15,9 @@ struct TaskWidgetProvider: TimelineProvider {
     }
 
     func getSnapshot(in context: Context, completion: @escaping (TaskWidgetEntry) -> ()) {
-        let tasks = DataCache.shared.allTasks.value as? [CustomTask] ?? []
+        // Note: Widgets run in a separate process and can't access shared app state directly.
+        // TODO: Implement App Groups or shared container for widget data access.
+        let tasks: [CustomTask] = []
         let entry = TaskWidgetEntry(
             date: Date(),
             tasks: Array(tasks.prefix(5))
@@ -24,7 +26,9 @@ struct TaskWidgetProvider: TimelineProvider {
     }
 
     func getTimeline(in context: Context, completion: @escaping (Timeline<TaskWidgetEntry>) -> ()) {
-        let tasks = DataCache.shared.allTasks.value as? [CustomTask] ?? []
+        // Note: Widgets run in a separate process and can't access shared app state directly.
+        // TODO: Implement App Groups or shared container for widget data access.
+        let tasks: [CustomTask] = []
         let entry = TaskWidgetEntry(
             date: Date(),
             tasks: Array(tasks.prefix(5))