Add encryption history banner and update session verification banner strings. (#1250)

* Add a hard wall on back-pagination in encrypted rooms.
Until the app supports key backup, the history will never be decryptable.

* Fix initial display of the timeline table view.

* Update session verification banner strings.

ElementX/Sources/Screens/Authentication/AuthenticationCoordinator.swift

@@ -205,6 +205,8 @@ class AuthenticationCoordinator: CoordinatorProtocol {
     }
     
     private func userHasSignedIn(userSession: UserSessionProtocol) {
+        appSettings.lastLoginDate = .now
+        
         showAnalyticsPromptIfNeeded { [weak self] in
             guard let self else { return }
             self.delegate?.authenticationCoordinator(self, didLoginWithSession: userSession)