feat: add complete Mayday iOS Xcode project

- Swift 6, SwiftUI, MVVM + async/await architecture
- iOS 17.0 minimum deployment target
- Two targets: Mayday app + MaydayLiveActivity widget extension
- Models: UserResponse, TokenPair, AppNotification, SessionResponse, AlertAttributes
- Services: HTTPClient (actor), AuthService, KeychainService, NotificationsAPIService, PushNotificationService
- ViewModels: AuthViewModel, NotificationsViewModel, SettingsViewModel
- Views: Login/Register/VerifyEmail, NotificationsList/Detail, Settings/ChangePassword/Sessions
- APNs push notifications with UIApplicationDelegate
- ActivityKit Live Activities for Dynamic Island + Lock Screen
- Keychain (Security framework) token storage
- 30-second polling with pagination for notifications
- Xcode project file (project.pbxproj) with correct build phases for both targets

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Mayday/Models/TokenPair.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+struct TokenPair: Codable {
+    let accessToken: String
+    let refreshToken: String
+    let expiresAt: Date
+    let tokenType: String
+
+    enum CodingKeys: String, CodingKey {
+        case accessToken = "access_token"
+        case refreshToken = "refresh_token"
+        case expiresAt = "expires_at"
+        case tokenType = "token_type"
+    }
+}