feat: unify language handling across the application

- Updated the language configuration to use a single source of truth from `DEFAULT_LANGUAGE` for the bot, API, and Mini App, eliminating auto-detection from user settings.
- Refactored the `get_lang` function to always return `DEFAULT_LANGUAGE`, ensuring consistent language usage throughout the application.
- Modified the handling of language in various components, including API responses and UI elements, to reflect the new language management approach.
- Enhanced documentation and comments to clarify the changes in language handling.
- Added unit tests to verify the new language handling behavior and ensure coverage for the updated functionality.

webapp/index.html

@@ -36,15 +36,66 @@
     <div id="currentDutyView" class="current-duty-view hidden"></div>
   </div>
   <script src="https://telegram.org/js/telegram-web-app.js"></script>
+  <script>
+    if (window.Telegram && window.Telegram.WebApp && window.Telegram.WebApp.ready) {
+      window.Telegram.WebApp.ready();
+    }
+  </script>
+  <script src="/app/config.js"></script>
   <script type="importmap">
   {
     "scopes": {
       "./js/": {
-        "./js/i18n.js": "./js/i18n.js?v=1"
+        "./js/api.js": "./js/api.js?v=3",
+        "./js/auth.js": "./js/auth.js?v=3",
+        "./js/calendar.js": "./js/calendar.js?v=2",
+        "./js/constants.js": "./js/constants.js?v=2",
+        "./js/contactHtml.js": "./js/contactHtml.js?v=2",
+        "./js/currentDuty.js": "./js/currentDuty.js?v=2",
+        "./js/dateUtils.js": "./js/dateUtils.js?v=2",
+        "./js/dayDetail.js": "./js/dayDetail.js?v=2",
+        "./js/dom.js": "./js/dom.js?v=3",
+        "./js/dutyList.js": "./js/dutyList.js?v=2",
+        "./js/hints.js": "./js/hints.js?v=2",
+        "./js/i18n.js": "./js/i18n.js?v=3",
+        "./js/theme.js": "./js/theme.js?v=2",
+        "./js/ui.js": "./js/ui.js?v=2",
+        "./js/utils.js": "./js/utils.js?v=2"
       }
     }
   }
   </script>
-  <script type="module" src="js/main.js?v=4"></script>
+  <script type="module" src="js/main.js?v=5" id="main-module"></script>
+  <script>
+    (function() {
+      var loadTimeout = 10000;
+      var mainScript = document.getElementById("main-module");
+      if (mainScript) {
+        mainScript.addEventListener("error", function() {
+          var loading = document.getElementById("loading");
+          if (loading && !loading.classList.contains("hidden")) {
+            loading.classList.add("hidden");
+            var err = document.getElementById("error");
+            if (err) {
+              err.hidden = false;
+              err.textContent = "Failed to load app. Check connection and try again.";
+            }
+          }
+        });
+      }
+      setTimeout(function() {
+        if (window.__dtReady) return;
+        var loading = document.getElementById("loading");
+        if (loading && !loading.classList.contains("hidden")) {
+          loading.classList.add("hidden");
+          var err = document.getElementById("error");
+          if (err) {
+            err.hidden = false;
+            err.textContent = "App is taking too long to load. Check your connection and refresh.";
+          }
+        }
+      }, loadTimeout);
+    })();
+  </script>
 </body>
 </html>