style: refine chat UI consistency and enhance dark mode (#393)

src/pages/Chat/index.tsx

@@ -77,18 +77,7 @@ export function Chat() {
     }
   }, [sending, streamingTimestamp]);
 
-  // Gateway not running
-  if (!isGatewayRunning) {
-    return (
-      <div className="flex h-[calc(100vh-8rem)] flex-col items-center justify-center text-center p-8">
-        <AlertCircle className="h-12 w-12 text-yellow-500 mb-4" />
-        <h2 className="text-xl font-semibold mb-2">{t('gatewayNotRunning')}</h2>
-        <p className="text-muted-foreground max-w-md">
-          {t('gatewayRequired')}
-        </p>
-      </div>
-    );
-  }
+  // Gateway not running block has been completely removed so the UI always renders.
 
   const streamMsg = streamingMessage && typeof streamingMessage === 'object'
     ? streamingMessage as unknown as { role?: string; content?: unknown; timestamp?: number }