Fix app.name override: use intl.addTranslations at runtime

Root cause: ember-intl merge order gives host app translations priority over
addon translations. The translations/en-us.yaml file was silently ignored.

Solution: Call intl.addTranslations('en-us', { 'app.name': 'Biibaye' })
at runtime from both setupExtension and onEngineLoaded hooks. This injects
the translation into the active intl service after the app boots.

Also removes the non-functional translations/en-us.yaml file.

addon/extension.js

@@ -3,15 +3,28 @@ export default {
         setDocumentTitle();
         injectBrandStyles();
         replaceFavicon();
+        overrideAppName(appInstance);
 
         universe.extensionManager.ensureEngineLoaded('@biibaye/branding');
     },
 
     onEngineLoaded(engineInstance, universe, appInstance) {
         setDocumentTitle();
+        overrideAppName(appInstance);
     },
 };
 
+function overrideAppName(appInstance) {
+    try {
+        const intl = appInstance.lookup('service:intl');
+        if (intl && typeof intl.addTranslations === 'function') {
+            intl.addTranslations('en-us', { 'app.name': 'Biibaye' });
+        }
+    } catch (e) {
+        // intl service not available yet — will retry in onEngineLoaded
+    }
+}
+
 function setDocumentTitle() {
     document.title = 'Biibaye - Delivery System';
 }