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/HeaderMoodLoggingTests.swift

@@ -0,0 +1,35 @@
+//
+//  HeaderMoodLoggingTests.swift
+//  Tests iOS
+//
+//  Header quick-entry mood logging tests.
+//
+
+import XCTest
+
+final class HeaderMoodLoggingTests: BaseUITestCase {
+    override var seedFixture: String? { "empty" }
+
+    /// TC-002: Log a mood from the header quick-entry and verify an entry row appears.
+    func testLogMood_FromHeader_CreatesEntry() {
+        let dayScreen = DayScreen(app: app)
+
+        // 1. Verify mood header is visible (empty state shows the voting header)
+        dayScreen.assertMoodHeaderVisible()
+
+        // 2. Tap "Good" mood button on the header
+        dayScreen.logMood(.good)
+
+        // 3. The header should disappear after the celebration animation
+        dayScreen.assertMoodHeaderHidden()
+
+        // 4. Verify an entry row appeared for today's date
+        let formatter = DateFormatter()
+        formatter.dateFormat = "M/d/yyyy"
+        let todayString = formatter.string(from: Date())
+
+        dayScreen.assertEntryExists(dateString: todayString)
+
+        captureScreenshot(name: "header_mood_logged_good")
+    }
+}