feat: complete Tasks 21-28 — backend integration, security hardening, UI tests & CI

- Add Apple Sign-In backend (JWKS verification, account linking, session management)
- Implement push notification deep linking with NotificationDeepLinkRouter
- Add jailbreak detection, runtime integrity monitoring, secure enclave service
- Implement OAuth social login, token refresh, and secure logout flows
- Add image caching (memory/disk), optimizer, upload queue, async semaphore
- Implement notification analytics, type preferences, and category setup
- Expand UI test suite with UITestBase, accessibility, auth flow, performance tests
- Add CI pipeline for iOS UI tests (3 device sizes) and performance benchmarks
- Restructure Xcode project to manual groups with KordantWidgets target
- Add SwiftLint, Swift Collections/Algorithms/GoogleSignIn dependencies
- Update project.yml for XcodeGen with new targets and configurations

iOS/Sources/Shared/WidgetDataManager.swift

@@ -0,0 +1,46 @@
+import Foundation
+
+/// Reads and writes WidgetData from the shared App Group UserDefaults container.
+/// Compiled into both the main app and widget extension targets.
+final class WidgetDataManager {
+    static let shared = WidgetDataManager()
+
+    private let suiteName = "group.com.frenocorp.kordant"
+    private let dataKey = "com.frenocorp.kordant.widgetData"
+
+    private init() {}
+
+    /// Persist widget data to the shared container.
+    func save(_ data: WidgetData) {
+        guard let defaults = UserDefaults(suiteName: suiteName) else {
+            assertionFailure("WidgetDataManager: Unable to access App Group UserDefaults")
+            return
+        }
+        do {
+            let encoded = try JSONEncoder().encode(data)
+            defaults.set(encoded, forKey: dataKey)
+        } catch {
+            assertionFailure("WidgetDataManager: Failed to encode widget data: \(error)")
+        }
+    }
+
+    /// Load widget data from the shared container.
+    /// Returns `nil` if no data has been written yet.
+    func load() -> WidgetData? {
+        guard let defaults = UserDefaults(suiteName: suiteName),
+              let data = defaults.data(forKey: dataKey) else {
+            return nil
+        }
+        do {
+            return try JSONDecoder().decode(WidgetData.self, from: data)
+        } catch {
+            assertionFailure("WidgetDataManager: Failed to decode widget data: \(error)")
+            return nil
+        }
+    }
+
+    /// Remove all stored widget data (e.g. on logout).
+    func clear() {
+        UserDefaults(suiteName: suiteName)?.removeObject(forKey: dataKey)
+    }
+}