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/MoodLoggingEmptyStateTests.swift

@@ -0,0 +1,36 @@
+//
+//  MoodLoggingEmptyStateTests.swift
+//  Tests iOS
+//
+//  Mood logging from empty state tests.
+//
+
+import XCTest
+
+final class MoodLoggingEmptyStateTests: BaseUITestCase {
+    override var seedFixture: String? { "empty" }
+
+    /// From empty state, log a "Great" mood -> entry row appears in the list.
+    func testLogMood_Great_FromEmptyState() {
+        let dayScreen = DayScreen(app: app)
+
+        // The mood header should be visible (empty state shows voting header)
+        dayScreen.assertMoodHeaderVisible()
+
+        // Tap "Great" mood button
+        dayScreen.logMood(.great)
+
+        // After logging, verify entry was created.
+        // The formatted date string depends on locale; verify at least
+        // one entry row exists via accessibility label containing "Great".
+        let greatEntry = app.descendants(matching: .any)
+            .matching(NSPredicate(format: "label CONTAINS[cd] %@", "Great"))
+            .firstMatch
+        XCTAssertTrue(
+            greatEntry.waitForExistence(timeout: 8),
+            "An entry labeled 'Great' should appear after logging"
+        )
+
+        captureScreenshot(name: "mood_logged_great")
+    }
+}