Add XCUITest suite with 27 test files covering unmapped P1 test cases

- Add 8 new test files: HeaderMoodLogging (TC-002), DayViewGrouping (TC-019),
  AllDayViewStyles (TC-021), MonthViewInteraction (TC-030), PaywallGate
  (TC-032/039/048), AppTheme (TC-070), IconPack (TC-072),
  PremiumCustomization (TC-075)
- Add accessibility IDs for paywall overlays, icon packs, app theme cards,
  and day view section headers
- Add --expire-trial launch argument to UITestMode for paywall gate testing
- Update QA test plan spreadsheet with XCUITest names for 14 test cases
- Include existing test infrastructure: screen objects, helpers, base class,
  and 19 previously written test files

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

Tests iOS/Helpers/WaitHelpers.swift

@@ -0,0 +1,65 @@
+//
+//  WaitHelpers.swift
+//  Tests iOS
+//
+//  Centralized, explicit wait helpers. No sleep() allowed.
+//
+
+import XCTest
+
+extension XCUIElement {
+
+    /// Wait for the element to exist in the hierarchy.
+    /// - Parameters:
+    ///   - timeout: Maximum seconds to wait.
+    ///   - message: Custom failure message.
+    /// - Returns: `true` if the element exists within the timeout.
+    @discardableResult
+    func waitForExistence(timeout: TimeInterval = 5, message: String? = nil) -> Bool {
+        let result = waitForExistence(timeout: timeout)
+        if !result, let message = message {
+            XCTFail(message)
+        }
+        return result
+    }
+
+    /// Wait until the element is hittable (exists and is enabled/visible).
+    /// - Parameter timeout: Maximum seconds to wait.
+    @discardableResult
+    func waitUntilHittable(timeout: TimeInterval = 5) -> Bool {
+        let predicate = NSPredicate(format: "isHittable == true")
+        let expectation = XCTNSPredicateExpectation(predicate: predicate, object: self)
+        let result = XCTWaiter.wait(for: [expectation], timeout: timeout)
+        return result == .completed
+    }
+
+    /// Tap the element after waiting for it to become hittable.
+    /// - Parameter timeout: Maximum seconds to wait before tapping.
+    func tapWhenReady(timeout: TimeInterval = 5, file: StaticString = #file, line: UInt = #line) {
+        guard waitUntilHittable(timeout: timeout) else {
+            XCTFail("Element \(identifier) not hittable after \(timeout)s", file: file, line: line)
+            return
+        }
+        tap()
+    }
+
+    /// Wait for the element to disappear from the hierarchy.
+    /// - Parameter timeout: Maximum seconds to wait.
+    @discardableResult
+    func waitForDisappearance(timeout: TimeInterval = 5) -> Bool {
+        let predicate = NSPredicate(format: "exists == false")
+        let expectation = XCTNSPredicateExpectation(predicate: predicate, object: self)
+        let result = XCTWaiter.wait(for: [expectation], timeout: timeout)
+        return result == .completed
+    }
+}
+
+extension XCUIApplication {
+
+    /// Wait for any element matching the identifier to exist.
+    func waitForElement(identifier: String, timeout: TimeInterval = 5) -> XCUIElement {
+        let element = descendants(matching: .any).matching(identifier: identifier).firstMatch
+        _ = element.waitForExistence(timeout: timeout)
+        return element
+    }
+}