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/AppThemeTests.swift

@@ -0,0 +1,125 @@
+//
+//  AppThemeTests.swift
+//  Tests iOS
+//
+//  App theme tests: browse themes sheet, verify all 12 theme cards exist,
+//  and apply a theme without crashing.
+//  TC-070
+//
+
+import XCTest
+
+final class AppThemeTests: BaseUITestCase {
+    override var seedFixture: String? { "single_mood" }
+    override var bypassSubscription: Bool { true }
+
+    /// All 12 app theme names (must match the accessibility IDs: apptheme_card_{lowercased name}).
+    private let allThemes = [
+        "Zen Garden", "Synthwave", "Celestial", "Editorial",
+        "Mixtape", "Bloom", "Heartfelt", "Minimal",
+        "Luxe", "Forecast", "Playful", "Journal"
+    ]
+
+    /// TC-070: Open Browse Themes sheet and verify all 12 theme cards exist.
+    func testBrowseThemes_AllCardsExist() {
+        let tabBar = TabBarScreen(app: app)
+        let settingsScreen = tabBar.tapSettings()
+        settingsScreen.assertVisible()
+
+        // Tap Browse Themes button
+        let browseButton = settingsScreen.browseThemesButton
+        XCTAssertTrue(
+            browseButton.waitForExistence(timeout: 5),
+            "Browse Themes button should exist"
+        )
+        browseButton.tapWhenReady()
+
+        // Wait for the themes sheet to appear
+        // Look for any theme card as an indicator that the sheet loaded
+        let firstCard = app.descendants(matching: .any)
+            .matching(identifier: "apptheme_card_zen garden")
+            .firstMatch
+        XCTAssertTrue(
+            firstCard.waitForExistence(timeout: 5),
+            "Themes sheet should appear with theme cards"
+        )
+
+        // Verify all 12 theme cards are accessible (some may require scrolling)
+        for theme in allThemes {
+            let card = app.descendants(matching: .any)
+                .matching(identifier: "apptheme_card_\(theme.lowercased())")
+                .firstMatch
+            if !card.exists {
+                // Scroll down to find cards that are off-screen
+                app.swipeUp()
+            }
+            XCTAssertTrue(
+                card.waitForExistence(timeout: 3),
+                "Theme card '\(theme)' should exist in the Browse Themes sheet"
+            )
+        }
+
+        captureScreenshot(name: "browse_themes_all_cards")
+    }
+
+    /// TC-070: Apply a representative set of themes and verify no crash.
+    func testApplyThemes_NoCrash() {
+        let tabBar = TabBarScreen(app: app)
+        let settingsScreen = tabBar.tapSettings()
+        settingsScreen.assertVisible()
+
+        // Open Browse Themes sheet
+        settingsScreen.browseThemesButton.tapWhenReady()
+
+        // Wait for sheet to load
+        let firstCard = app.descendants(matching: .any)
+            .matching(identifier: "apptheme_card_zen garden")
+            .firstMatch
+        _ = firstCard.waitForExistence(timeout: 5)
+
+        // Tap a representative sample of themes: first, middle, last
+        let sampled = ["Zen Garden", "Heartfelt", "Journal"]
+        for theme in sampled {
+            let card = app.descendants(matching: .any)
+                .matching(identifier: "apptheme_card_\(theme.lowercased())")
+                .firstMatch
+            if !card.exists {
+                app.swipeUp()
+            }
+            if card.waitForExistence(timeout: 3) {
+                card.tapWhenReady()
+
+                // A preview sheet or confirmation may appear — dismiss it
+                // Look for an "Apply" or close button and tap if present
+                let applyButton = app.buttons["Apply"]
+                if applyButton.waitForExistence(timeout: 2) {
+                    applyButton.tapWhenReady()
+                }
+            }
+        }
+
+        captureScreenshot(name: "themes_applied")
+
+        // Dismiss the themes sheet by swiping down or tapping Done
+        let doneButton = app.buttons["Done"]
+        if doneButton.waitForExistence(timeout: 2) {
+            doneButton.tapWhenReady()
+        } else {
+            // Swipe down to dismiss the sheet
+            app.swipeDown()
+        }
+
+        // Navigate to Day tab and verify no crash — entry row should still exist
+        tabBar.tapDay()
+
+        let entryRow = app.descendants(matching: .any)
+            .matching(NSPredicate(format: "identifier BEGINSWITH %@", "entry_row_"))
+            .firstMatch
+        XCTAssertTrue(
+            entryRow.waitForExistence(timeout: 5),
+            "Entry row should still be visible after applying themes (no crash)"
+        )
+
+        captureScreenshot(name: "day_view_after_theme_change")
+    }
+}