ui: expose i18n via window, add cache-busting query strings

internal/webapp/static/i18n.js

@@ -1,4 +1,4 @@
-const i18n = {
+var i18n = {
   ko: {
     eyebrow: "튜터 플랫폼",
     titleLogin: "면접 연습",
@@ -172,7 +172,7 @@ const i18n = {
   },
 };
 
-function t(key, ...args) {
+window.t = function (key, ...args) {
   const lang =
     localStorage.getItem("tutor_lang") ||
     document.documentElement.lang ||
@@ -181,7 +181,7 @@ function t(key, ...args) {
   return typeof text === "function" ? text(...args) : text;
 }
 
-function updateStaticText() {
+window.updateStaticText = function () {
   const lang =
     localStorage.getItem("tutor_lang") ||
     document.documentElement.lang ||