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>

Shared/Onboarding/views/OnboardingDay.swift

@@ -73,7 +73,8 @@ struct OnboardingDay: View {
                         example: "e.g. Tue reminder → Rate Tue",
                         icon: "sun.max.fill",
                         isSelected: onboardingData.inputDay == .Today,
-                        action: { onboardingData.inputDay = .Today }
+                        action: { onboardingData.inputDay = .Today },
+                        testID: AccessibilityID.Onboarding.dayToday
                     )
 
                     DayOptionCard(
@@ -82,7 +83,8 @@ struct OnboardingDay: View {
                         example: "e.g. Tue reminder → Rate Mon",
                         icon: "moon.fill",
                         isSelected: onboardingData.inputDay == .Previous,
-                        action: { onboardingData.inputDay = .Previous }
+                        action: { onboardingData.inputDay = .Previous },
+                        testID: AccessibilityID.Onboarding.dayYesterday
                     )
                 }
                 .padding(.horizontal, 20)
@@ -103,6 +105,7 @@ struct OnboardingDay: View {
                 .padding(.bottom, 80)
             }
         }
+        .accessibilityIdentifier(AccessibilityID.Onboarding.dayScreen)
     }
 }
 
@@ -113,6 +116,7 @@ struct DayOptionCard: View {
     let icon: String
     let isSelected: Bool
     let action: () -> Void
+    var testID: String? = nil
 
     var body: some View {
         Button(action: action) {
@@ -168,6 +172,7 @@ struct DayOptionCard: View {
         .accessibilityLabel("\(title), \(subtitle)")
         .accessibilityHint(example)
         .accessibilityAddTraits(isSelected ? [.isSelected] : [])
+        .accessibilityIdentifier(testID ?? "")
     }
 }