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/MockPlantClassificationService.swift

@@ -87,6 +87,12 @@ final actor MockPlantClassificationService: PlantClassificationServiceProtocol {
         ]
     }
 
+    /// Configures throw behavior from outside the actor
+    func setThrowBehavior(shouldThrow: Bool, error: Error) {
+        shouldThrowOnClassify = shouldThrow
+        errorToThrow = error
+    }
+
     /// Configures low confidence predictions for testing fallback behavior
     func configureLowConfidencePredictions() {
         predictionsToReturn = [