Add iOS lifecycle hardening hooks

apps/ios/TeleTuiIOS/Sources/TeleTuiIOSCore/Lifecycle.swift

@@ -0,0 +1,53 @@
+import Foundation
+
+public enum AppLifecycleState: Equatable, Sendable {
+    case foreground
+    case background
+}
+
+public struct ScopedSessionEvent: Equatable, Sendable {
+    public var accountId: String
+    public var generation: Int
+    public var event: SessionEvent
+
+    public init(accountId: String, generation: Int, event: SessionEvent) {
+        self.accountId = accountId
+        self.generation = generation
+        self.event = event
+    }
+}
+
+@MainActor
+public final class SessionLifecycleCoordinator: ObservableObject {
+    @Published public private(set) var lifecycleState: AppLifecycleState = .foreground
+    @Published public private(set) var activeAccountId: String
+    @Published public private(set) var generation = 0
+
+    public init(activeAccountId: String) {
+        self.activeAccountId = activeAccountId
+    }
+
+    public var shouldPollEvents: Bool {
+        lifecycleState == .foreground
+    }
+
+    public func enterBackground() {
+        lifecycleState = .background
+    }
+
+    public func enterForeground() {
+        lifecycleState = .foreground
+    }
+
+    public func switchAccount(to accountId: String) {
+        guard accountId != activeAccountId else {
+            return
+        }
+        activeAccountId = accountId
+        generation += 1
+    }
+
+    public func accepts(_ event: ScopedSessionEvent) -> Bool {
+        event.accountId == activeAccountId && event.generation == generation
+    }
+}