fix: address all PR review comments

- HTTPClient: replace isRefreshing bool with shared Task to safely
  coalesce concurrent 401 refresh attempts; surface JSON serialization
  error instead of silently dropping request body
- AuthService.logout: always clear Keychain tokens via defer, even when
  refresh token is absent, preventing stale access token
- NotificationsAPIService: remove updateAppBadge (UIKit call moved to
  @MainActor NotificationsViewModel); drop unused UIKit import
- NotificationsViewModel: guard startPolling() against duplicate tasks;
  update badge directly on @MainActor instead of hopping to actor
- VerifyEmailView: replace Timer (never invalidated) with async Task
  cancelled in .onDisappear
- NotificationsView: use Text(date, style: .relative) — auto-updates
  without custom formatter; remove duplicate Date extension
- SettingsView: handle logoutAll errors explicitly with alert instead of
  silently proceeding with local logout
- MaydayLiveActivity/Info.plist: add NSExtensionPrincipalClass so the
  widget extension is discoverable by the system
- Live Activity widget: replace frozen duration(from:) with
  Text(date, style: .timer); replace frozen relativeFormatted with
  Text(date, style: .relative); localize status badge to Russian

Co-authored-by: robonen <26167508+robonen@users.noreply.github.com>

Mayday/Views/Settings/SettingsView.swift

@@ -7,6 +7,7 @@ struct SettingsView: View {
     @State private var showChangePassword = false
     @State private var showSessions = false
     @State private var showLogoutAllConfirm = false
+    @State private var logoutAllError: String?
 
     var body: some View {
         NavigationStack {
@@ -81,12 +82,27 @@ struct SettingsView: View {
             ) {
                 Button("Выйти везде", role: .destructive) {
                     Task {
-                        _ = try? await NotificationsAPIService.shared.logoutAll()
-                        await authViewModel.logout()
+                        do {
+                            _ = try await NotificationsAPIService.shared.logoutAll()
+                            await authViewModel.logout()
+                        } catch {
+                            logoutAllError = error.localizedDescription
+                        }
                     }
                 }
                 Button("Отмена", role: .cancel) {}
             }
+            .alert(
+                "Ошибка",
+                isPresented: Binding(
+                    get: { logoutAllError != nil },
+                    set: { if !$0 { logoutAllError = nil } }
+                )
+            ) {
+                Button("OK") { logoutAllError = nil }
+            } message: {
+                Text(logoutAllError ?? "")
+            }
             .task {
                 await viewModel.loadSessions()
             }