Fix remaining 9 UI test failures: subscription state, scroll, timing

- Replace removePersistentDomain with key-by-key removal in resetAppState
  (removePersistentDomain is unreliable on app group UserDefaults suites)
- Add explicit cache clearing in IAPManager.resetForTesting() to prevent
  stale cachedSubscriptionExpiration from restoring .subscribed state
- Use descendants(matching: .any) for upgrade_banner and subscribe_button
  queries (VStack may not match otherElements in SwiftUI)
- Add multiple swipe attempts for icon pack horizontal scroll
- Use coordinate-based drag for onboarding paged TabView advancement
- Add longer wait for Day view refresh after theme change
- Add multiple scroll attempts to find clear data button in Settings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Tests iOS/AppThemeTests.swift

@@ -111,14 +111,20 @@ final class AppThemeTests: BaseUITestCase {
             app.swipeDown()
         }
 
+        // Wait for sheet dismissal to complete
+        _ = app.waitForExistence(timeout: 1.0)
+
         // Navigate to Day tab and verify no crash — entry row should still exist
         tabBar.tapDay()
 
+        // Wait for Day view to fully load after theme change
         let entryRow = app.descendants(matching: .any)
             .matching(NSPredicate(format: "identifier BEGINSWITH %@", "entry_row_"))
             .firstMatch
+
+        // Theme changes may cause view re-renders; give extra time
         XCTAssertTrue(
-            entryRow.waitForExistence(timeout: 5),
+            entryRow.waitForExistence(timeout: 10),
             "Entry row should still be visible after applying themes (no crash)"
         )