Fix mCaptcha broken after Vite migration (#37492)

After the Webpack-to-Vite migration (#37002), mCaptcha stopped working
entirely on the registration page, throwing an error:

`TypeError: setting getter-only property "INPUT_NAME"`

This fix stops trying to mutate the read-only INPUT_NAME export. Instead
it probes for the Widget constructor at module.default (direct) or
module.default.default (CJS-wrapped), constructs the widget, and then
renames the hidden input element it creates to m-captcha-response which
is the field name Gitea's backend reads from the submitted form.

Generative AI was used to help with making this PR.

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

package.json

@@ -26,7 +26,7 @@
     "@github/paste-markdown": "1.5.3",
     "@github/text-expander-element": "2.9.4",
     "@lezer/highlight": "1.2.3",
-    "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
+    "@mcaptcha/vanilla-glue": "0.1.0-rc2",
     "@mermaid-js/layout-elk": "0.2.1",
     "@primer/octicons": "19.24.1",
     "@replit/codemirror-indentation-markers": "6.5.3",