refactor: tighten types and reuse instrument UI

src/app/routes/AppRoutes/AppRoutes.test.tsx

@@ -65,6 +65,8 @@ describe("AppRoutes", () => {
 			path: { pathname: "/login", state: { returnTo: "//example.com" } },
 			title: "Вход",
 		},
+		{ endpoint: "login", path: { pathname: "/login", state: { returnTo: 42 } }, title: "Вход" },
+		{ endpoint: "login", path: { pathname: "/login", state: 42 }, title: "Вход" },
 	])("authenticates via $endpoint and reaches the protected landing from $path", async ({ endpoint, path, title }) => {
 		let credentials: unknown;
 		server.use(

src/app/routes/RouteErrorBoundary/RouteErrorBoundary.tsx

@@ -24,15 +24,15 @@ class Boundary extends Component<BoundaryProps, State> {
 		return { hasError: true };
 	}
 
-	state: State = { hasError: false };
+	override state: State = { hasError: false };
 
-	componentDidUpdate(previousProps: BoundaryProps) {
+	override componentDidUpdate(previousProps: BoundaryProps) {
 		if (previousProps.routeKey !== this.props.routeKey && this.state.hasError) {
 			this.setState({ hasError: false });
 		}
 	}
 
-	render() {
+	override render() {
 		return this.state.hasError
 			? <RouteErrorFallback authenticated={this.props.authenticated} />
 			: (

src/app/routes/RouteGuards.tsx

@@ -30,8 +30,11 @@ const Public: FC<PropsWithChildren> = (props) => {
 
 	if (!ready) return <RouteSkeleton variant="shell" />;
 
-	const requested = (location.state as null
-		| { returnTo?: string })?.returnTo;
+	const state: unknown = location.state;
+
+	const requested = state && typeof state === "object" && "returnTo" in state
+		? state.returnTo
+		: undefined;
 
 	const returnTo
 		= typeof requested === "string"