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/DayViewGroupingTests.swift

@@ -0,0 +1,51 @@
+//
+//  DayViewGroupingTests.swift
+//  Tests iOS
+//
+//  Day view section header grouping tests.
+//
+
+import XCTest
+
+final class DayViewGroupingTests: BaseUITestCase {
+    override var seedFixture: String? { "week_of_moods" }
+
+    /// TC-019: Entries are grouped by year/month section headers.
+    func testEntries_GroupedBySectionHeaders() {
+        // 1. Wait for entry list to load with seeded data
+        let firstEntry = app.descendants(matching: .any)
+            .matching(NSPredicate(format: "identifier BEGINSWITH %@", "entry_row_"))
+            .firstMatch
+        XCTAssertTrue(
+            firstEntry.waitForExistence(timeout: 5),
+            "Entry rows should exist with week_of_moods fixture"
+        )
+
+        // 2. Verify at least one section header exists
+        let anySectionHeader = app.descendants(matching: .any)
+            .matching(NSPredicate(format: "identifier BEGINSWITH %@", "day_section_"))
+            .firstMatch
+        XCTAssertTrue(
+            anySectionHeader.waitForExistence(timeout: 5),
+            "At least one day_section_ header should exist"
+        )
+
+        // 3. The week_of_moods fixture contains entries in the current month.
+        //    Verify the section header for the current month/year exists.
+        let now = Date()
+        let calendar = Calendar.current
+        let month = calendar.component(.month, from: now)
+        let year = calendar.component(.year, from: now)
+
+        let expectedHeaderID = "day_section_\(month)_\(year)"
+        let currentMonthHeader = app.descendants(matching: .any)
+            .matching(identifier: expectedHeaderID)
+            .firstMatch
+        XCTAssertTrue(
+            currentMonthHeader.waitForExistence(timeout: 5),
+            "Section header '\(expectedHeaderID)' should exist for current month"
+        )
+
+        captureScreenshot(name: "day_view_section_headers")
+    }
+}