feat: hide empty-state placeholder in email viewer pane

components/email/email-viewer.tsx

@@ -3252,21 +3252,7 @@ export function EmailViewer({
       );
     }
     return (
-      <div className={cn("flex-1 flex flex-col items-center justify-center bg-gradient-to-br from-muted/30 to-muted/50", className)}>
-        <div className="text-center p-8">
-          <div className="w-20 h-20 mx-auto mb-6 rounded-full bg-background shadow-lg flex items-center justify-center">
-            <Mail className="w-10 h-10 text-muted-foreground" />
-          </div>
-          <h3 className="text-xl font-semibold text-foreground mb-2">{t('no_conversation_selected')}</h3>
-          <p className="text-muted-foreground">{t('no_conversation_description')}</p>
-          {onCompose && (
-            <Button onClick={onCompose} className="mt-6" title={t('compose_hint')}>
-              <PenSquare className="w-4 h-4 mr-2" />
-              {t('compose')}
-            </Button>
-          )}
-        </div>
-      </div>
+      <div className={cn("flex-1 flex flex-col items-center justify-center bg-gradient-to-br from-muted/30 to-muted/50", className)} />
     );
   }