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/BaseUITestCase.swift

@@ -0,0 +1,81 @@
+//
+//  BaseUITestCase.swift
+//  Tests iOS
+//
+//  Base class for all UI tests. Handles launch arguments,
+//  state reset, and screenshot capture on failure.
+//
+
+import XCTest
+
+class BaseUITestCase: XCTestCase {
+
+    var app: XCUIApplication!
+
+    // MARK: - Configuration (override in subclasses)
+
+    /// Fixture to seed. Override to use a specific data set.
+    var seedFixture: String? { nil }
+
+    /// Whether to bypass the subscription paywall. Default: true.
+    var bypassSubscription: Bool { true }
+
+    /// Whether to skip onboarding. Default: true.
+    var skipOnboarding: Bool { true }
+
+    /// Whether to force the trial to be expired. Default: false.
+    var expireTrial: Bool { false }
+
+    // MARK: - Lifecycle
+
+    override func setUp() {
+        super.setUp()
+        continueAfterFailure = false
+
+        app = XCUIApplication()
+        app.launchArguments = buildLaunchArguments()
+        app.launchEnvironment = buildLaunchEnvironment()
+        app.launch()
+    }
+
+    override func tearDown() {
+        if let failure = testRun?.failureCount, failure > 0 {
+            captureScreenshot(name: "FAILURE-\(name)")
+        }
+        app = nil
+        super.tearDown()
+    }
+
+    // MARK: - Launch Configuration
+
+    private func buildLaunchArguments() -> [String] {
+        var args = ["--ui-testing", "--reset-state", "--disable-animations"]
+        if bypassSubscription {
+            args.append("--bypass-subscription")
+        }
+        if skipOnboarding {
+            args.append("--skip-onboarding")
+        }
+        if expireTrial {
+            args.append("--expire-trial")
+        }
+        return args
+    }
+
+    private func buildLaunchEnvironment() -> [String: String] {
+        var env = [String: String]()
+        if let fixture = seedFixture {
+            env["UI_TEST_FIXTURE"] = fixture
+        }
+        return env
+    }
+
+    // MARK: - Screenshots
+
+    func captureScreenshot(name: String) {
+        let screenshot = XCTAttachment(screenshot: app.screenshot())
+        screenshot.name = name
+        screenshot.lifetime = .keepAlways
+        add(screenshot)
+    }
+}