Add base web UI

moneymgr_web/src/widgets/AuthSingleMessage.tsx

@@ -0,0 +1,13 @@
+import { Button } from "@mui/material";
+import { Link } from "react-router-dom";
+
+export function AuthSingleMessage(p: { message: string }): React.ReactElement {
+  return (
+    <>
+      <p style={{ textAlign: "center" }}>{p.message}</p>
+      <Link to={"/"}>
+        <Button>Go back home</Button>
+      </Link>
+    </>
+  );
+}