fixed broken second counter in no-JS mode

src/backend/components/counter.tsx

@@ -2,7 +2,7 @@ import type { Request } from "express";
 import { safeGetQueryValue } from "../utils.ts";
 
 export const getCounterHtml = (req: Request, key: string) => {
-  const counter = parseInt(safeGetQueryValue(req, "a") ?? "0", 10);
+  const counter = parseInt(safeGetQueryValue(req, key) ?? "0", 10);
   return (
     <>
       <form method="post" is="progressive-form">