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>

PlantGuideUITests/Foundation/BaseUITestCase.swift

@@ -0,0 +1,88 @@
+//
+//  BaseUITestCase.swift
+//  PlantGuideUITests
+//
+//  Base class for all PlantGuide UI tests.
+//  Provides deterministic launch, fixture control, and shared helpers.
+//
+
+import XCTest
+
+/// Base class every UI test class should inherit from.
+///
+/// Provides:
+/// - Deterministic `app` instance with clean lifecycle
+/// - Convenience launchers for clean state, mock data, offline
+/// - Tab navigation via `navigateToTab(_:)`
+/// - Implicit `waitForLaunch()` after every launch helper
+class BaseUITestCase: XCTestCase {
+
+    // MARK: - Properties
+
+    /// The application under test. Reset for each test method.
+    var app: XCUIApplication!
+
+    // MARK: - Lifecycle
+
+    override func setUpWithError() throws {
+        try super.setUpWithError()
+        continueAfterFailure = false
+        app = XCUIApplication()
+    }
+
+    override func tearDownWithError() throws {
+        app = nil
+        try super.tearDownWithError()
+    }
+
+    // MARK: - Launch Helpers
+
+    /// Launches with a fresh database and no prior state.
+    func launchClean() {
+        app.launchArguments += [
+            LaunchConfigKey.uiTesting,
+            LaunchConfigKey.cleanState,
+            LaunchConfigKey.skipOnboarding
+        ]
+        app.launchEnvironment[LaunchConfigKey.isUITesting] = "YES"
+        app.launch()
+        XCTAssertTrue(app.waitForLaunch(timeout: 15), "App did not launch (clean)")
+    }
+
+    /// Launches with mock plants and care data pre-populated.
+    func launchWithMockData(plantCount: Int = 5) {
+        app.launchArguments += [
+            LaunchConfigKey.uiTesting,
+            LaunchConfigKey.mockData,
+            LaunchConfigKey.skipOnboarding
+        ]
+        app.launchEnvironment[LaunchConfigKey.isUITesting] = "YES"
+        app.launchEnvironment[LaunchConfigKey.useMockData] = "YES"
+        app.launchEnvironment["MOCK_PLANT_COUNT"] = String(plantCount)
+        app.launch()
+        XCTAssertTrue(app.waitForLaunch(timeout: 15), "App did not launch (mock data)")
+    }
+
+    /// Launches simulating no network.
+    func launchOffline() {
+        app.launchArguments += [
+            LaunchConfigKey.uiTesting,
+            LaunchConfigKey.offlineMode,
+            LaunchConfigKey.skipOnboarding
+        ]
+        app.launchEnvironment[LaunchConfigKey.isUITesting] = "YES"
+        app.launchEnvironment[LaunchConfigKey.isOfflineMode] = "YES"
+        app.launch()
+        XCTAssertTrue(app.waitForLaunch(timeout: 15), "App did not launch (offline)")
+    }
+
+    // MARK: - Tab Navigation
+
+    /// Taps a tab by its label (use `UITestID.TabBar.*`).
+    func navigateToTab(_ tabLabel: String) {
+        let tab = app.tabBars.buttons[tabLabel]
+        XCTAssertTrue(tab.waitForExistence(timeout: 10),
+                      "Tab '\(tabLabel)' not found")
+        tab.tap()
+    }
+}