fix: correct locale format from en-us to en-US

- Fixed ember-intl locale format to use proper case (en-US)
- Renamed translation file: en-us.yaml → en-US.yaml
- Updated fallbackLocale in ember-intl config
- Updated default locale in application route
- Fixes MISSING_DATA error in Intl.NumberFormat

The Intl API requires proper locale format (en-US not en-us)

console/app/routes/application.js

@@ -124,11 +124,11 @@ export default class ApplicationRoute extends Route {
      * Initializes the application's locale settings based on the current user's preferences.
      *
      * This method retrieves the user's preferred locale using the `getOption` method from the `currentUser` service.
-     * If no locale is set by the user, it defaults to `'en-us'`. It then sets the application's locale by calling
+     * If no locale is set by the user, it defaults to `'en-US'`. It then sets the application's locale by calling
      * the `setLocale` method of the `intl` service with the retrieved locale.
      */
     initializeLocale() {
-        const locale = this.currentUser.getOption('locale', 'en-us');
+        const locale = this.currentUser.getOption('locale', 'en-US');
         this.intl.setLocale([locale]);
     }
 

console/config/ember-intl.js

@@ -14,7 +14,7 @@ module.exports = function (/* environment */) {
          * @type {String?}
          * @default "null"
          */
-        fallbackLocale: 'en-us',
+        fallbackLocale: 'en-US',
 
         /**
          * Path where translations are stored.  This is relative to the project root.