Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/features/captcha.ts

@@ -0,0 +1,51 @@
+import {isDarkTheme} from '../utils.ts';
+
+export async function initCaptcha() {
+  const captchaEl = document.querySelector('#captcha');
+  if (!captchaEl) return;
+
+  const siteKey = captchaEl.getAttribute('data-sitekey');
+  const isDark = isDarkTheme();
+
+  const params = {
+    sitekey: siteKey,
+    theme: isDark ? 'dark' : 'light',
+  };
+
+  switch (captchaEl.getAttribute('data-captcha-type')) {
+    case 'g-recaptcha': {
+      if (window.grecaptcha) {
+        window.grecaptcha.ready(() => {
+          window.grecaptcha.render(captchaEl, params);
+        });
+      }
+      break;
+    }
+    case 'cf-turnstile': {
+      if (window.turnstile) {
+        window.turnstile.render(captchaEl, params);
+      }
+      break;
+    }
+    case 'h-captcha': {
+      if (window.hcaptcha) {
+        window.hcaptcha.render(captchaEl, params);
+      }
+      break;
+    }
+    case 'm-captcha': {
+      const {default: mCaptcha} = await import(/* webpackChunkName: "mcaptcha-vanilla-glue" */'@mcaptcha/vanilla-glue');
+      mCaptcha.INPUT_NAME = 'm-captcha-response';
+      const instanceURL = captchaEl.getAttribute('data-instance-url');
+
+      mCaptcha.default({
+        siteKey: {
+          instanceUrl: new URL(instanceURL),
+          key: siteKey,
+        },
+      });
+      break;
+    }
+    default:
+  }
+}