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/Screens/TabBarScreen.swift

@@ -0,0 +1,77 @@
+//
+//  TabBarScreen.swift
+//  PlantGuideUITests
+//
+//  Screen object for the main tab bar.
+//
+
+import XCTest
+
+struct TabBarScreen {
+    let app: XCUIApplication
+
+    // MARK: - Elements
+
+    var tabBar: XCUIElement { app.tabBars.firstMatch }
+    var cameraTab: XCUIElement { tabBar.buttons[UITestID.TabBar.camera] }
+    var collectionTab: XCUIElement { tabBar.buttons[UITestID.TabBar.collection] }
+    var todayTab: XCUIElement { tabBar.buttons[UITestID.TabBar.today] }
+    var settingsTab: XCUIElement { tabBar.buttons[UITestID.TabBar.settings] }
+
+    var allTabLabels: [String] {
+        [UITestID.TabBar.camera,
+         UITestID.TabBar.collection,
+         UITestID.TabBar.today,
+         UITestID.TabBar.settings]
+    }
+
+    // MARK: - Actions
+
+    /// Taps a tab button using existence-based wait (not hittable — tab bar buttons
+    /// report isHittable == false in iOS 26 simulator despite being tappable).
+    private func tapTab(_ tab: XCUIElement) {
+        XCTAssertTrue(tab.waitForExistence(timeout: 10),
+                      "Tab '\(tab.label)' not found within 10s")
+        tab.tap()
+    }
+
+    @discardableResult
+    func tapCamera() -> CameraScreen {
+        tapTab(cameraTab)
+        return CameraScreen(app: app)
+    }
+
+    @discardableResult
+    func tapCollection() -> CollectionScreen {
+        tapTab(collectionTab)
+        return CollectionScreen(app: app)
+    }
+
+    @discardableResult
+    func tapToday() -> TodayScreen {
+        tapTab(todayTab)
+        return TodayScreen(app: app)
+    }
+
+    @discardableResult
+    func tapSettings() -> SettingsScreen {
+        tapTab(settingsTab)
+        return SettingsScreen(app: app)
+    }
+
+    // MARK: - Assertions
+
+    func assertAllTabsExist() {
+        XCTAssertTrue(tabBar.waitForExistence(timeout: 10), "Tab bar missing")
+        for label in allTabLabels {
+            XCTAssertTrue(tabBar.buttons[label].waitForExistence(timeout: 5),
+                          "Tab '\(label)' missing")
+        }
+    }
+
+    func assertSelected(_ label: String) {
+        let tab = tabBar.buttons[label]
+        XCTAssertTrue(tab.waitForExistence(timeout: 5), "Tab '\(label)' not found")
+        XCTAssertTrue(tab.isSelected, "Tab '\(label)' not selected")
+    }
+}