feat(ui): 添加配置错误 toast 提示

当 Provider API Key 未配置时，显示 toast 提示并提供
"去配置"按钮，点击可直接打开 Providers 配置面板

packages/web/src/pages/Chat.tsx

@@ -5,6 +5,7 @@
 import { useEffect, useRef } from 'react';
 import { WifiOff, MessageSquare, Settings, FolderOpen, Terminal, Plug, Zap, Bot, History, Server } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
+import { toast } from 'sonner';
 import {
   useChat,
   ChatMessage,
@@ -64,6 +65,17 @@ export function ChatPage({
     },
     onSessionNotFound,
     onSessionUpdated,
+    onConfigError: (error) => {
+      toast.error(error.message, {
+        duration: 10000,
+        action: onOpenProviders
+          ? {
+              label: '去配置',
+              onClick: onOpenProviders,
+            }
+          : undefined,
+      });
+    },
   });
 
   const messagesEndRef = useRef<HTMLDivElement>(null);