build: pagecheck as standalone node script (inline escaping was fragile)

scripts/pagecheck.js

@@ -0,0 +1,23 @@
+// pagecheck: syntax-check the embedded quota page JS (guards against
+// parse-time SyntaxErrors like duplicate const that break the whole page).
+const fs = require("fs");
+const src = fs.readFileSync("plugin/quota_page.go", "utf8");
+const m = src.match(/const QuotaPageHTML = `([\s\S]*)`/);
+if (!m) {
+  console.error("pagecheck: QuotaPageHTML not found");
+  process.exit(1);
+}
+const js = [...m[1].matchAll(/<script>([\s\S]*?)<\/script>/g)]
+  .map((x) => x[1])
+  .join("\n");
+if (!js.trim()) {
+  console.error("pagecheck: no <script> content found");
+  process.exit(1);
+}
+try {
+  new Function(js);
+} catch (e) {
+  console.error("pagecheck: embedded JS SyntaxError:", e.message);
+  process.exit(1);
+}
+console.log("pagecheck: embedded JS syntax OK");