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/iosApp/Localizable.xcstrings

@@ -16890,6 +16890,9 @@
     "Done" : {
       "comment" : "A button that dismisses an image viewer sheet.",
       "isCommentAutoGenerated" : true
+    },
+    "Downloading..." : {
+
     },
     "Edit" : {
       "comment" : "A label for an edit action.",
@@ -29458,10 +29461,6 @@
     },
     "Unarchive Task" : {
 
-    },
-    "Upgrade to Pro" : {
-      "comment" : "A button label that says \"Upgrade to Pro\".",
-      "isCommentAutoGenerated" : true
     },
     "Upgrade to Pro for unlimited access" : {
       "comment" : "A description of the benefit of upgrading to the Pro plan.",