Fix 4 flaky UI tests for iOS 26 compatibility

- AppLaunchTests/StabilityTests: Increase assertTabSelected timeout to
  8s for iOS 26 Liquid Glass delayed isSelected state updates
- DeepLinkTests: Detect SubscriptionStoreView container instead of text
  labels, since Apple's native view shows "Subscription Unavailable" in
  test storefront
- SettingsActionTests: Check for empty state after clearing data, bump
  Settings header timeout to 8s

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

Tests iOS/SettingsActionTests.swift

@@ -45,10 +45,14 @@ final class SettingsActionTests: BaseUITestCase {
         tabBar.tapDay()
 
         // App should remain usable after clearing data.
-        assertDayContentVisible(timeout: 10)
+        // After a full clear, Day view may show mood header, entry rows, or empty state.
+        let hasEntry = app.firstEntryRow.waitForExistence(timeout: 10)
+        let hasMoodHeader = app.element(UITestID.Day.moodHeader).waitForExistence(timeout: 2)
+        let hasEmptyState = app.element(UITestID.Day.emptyStateNoData).waitForExistence(timeout: 2)
+        XCTAssertTrue(hasEntry || hasMoodHeader || hasEmptyState,
+            "Day view should show entries, mood header, or empty state after clearing data")
 
-        // Clear action should not crash the app, even if the resulting day content
-        // is rehydrated by app-specific defaults/placeholders.
+        // Clear action should not crash the app.
         XCTAssertTrue(app.tabBars.firstMatch.exists, "App should remain responsive after clearing data")
 
         captureScreenshot(name: "data_cleared")