Rebuild UI test foundation with page objects, wait helpers, and screen objects

Replace brittle localized-string selectors and broken wait helpers with a
robust, identifier-first UI test infrastructure. All 41 UI tests pass on
iOS 26.2 simulator (iPhone 17).

Foundation:
- BaseUITestCase with deterministic launch helpers (launchClean, launchOffline)
- WaitHelpers (waitUntilHittable, waitUntilGone, tapWhenReady) replacing sleep()
- UITestID enum mirroring AccessibilityIdentifiers from the app target
- Screen objects: TabBarScreen, CameraScreen, CollectionScreen, TodayScreen,
  SettingsScreen, PlantDetailScreen

Key fixes:
- Tab navigation uses waitForExistence+tap instead of isHittable (unreliable
  in iOS 26 simulator)
- Tests handle real app state (empty collection, no camera permission)
- Increased timeouts for parallel clone execution
- Added NetworkMonitorProtocol and protocol-typed DI for testability
- Fixed actor-isolation issues in unit test mocks

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PlantGuideTests/Mocks/MockNotificationService.swift

@@ -131,6 +131,14 @@ final actor MockNotificationService: NotificationServiceProtocol {
         removeAllDeliveredNotificationsCallCount += 1
     }
 
+    func schedulePhotoReminder(for plantID: UUID, plantName: String, interval: PhotoReminderInterval) async throws {
+        // no-op for tests
+    }
+
+    func cancelPhotoReminder(for plantID: UUID) async {
+        // no-op for tests
+    }
+
     // MARK: - Helper Methods
 
     /// Resets all state for clean test setup