style(frontend):优化前端效果

1.对于UI的配色和布局进行了优化

frontend/src/App.tsx

@@ -28,7 +28,6 @@ function App() {
 
   const { loadSessions } = useChatStore();
 
-  // Initialize theme on mount
   useEffect(() => {
     applyTheme();
     const mediaQuery = window.matchMedia('(prefers-color-scheme: dark)');
@@ -37,14 +36,12 @@ function App() {
     return () => mediaQuery.removeEventListener('change', handler);
   }, [applyTheme]);
 
-  // Sync persisted locale to i18next on mount
   useEffect(() => {
     if (locale && i18n.language !== locale) {
       i18n.changeLanguage(locale);
     }
   }, [locale]);
 
-  // Check auth and load sessions
   useEffect(() => {
     const token = localStorage.getItem('token');
     if (token) {
@@ -75,11 +72,9 @@ function App() {
 
             <div className="flex-1 flex overflow-hidden">
               {mode === 'work' && workTab === 'chat' && (
-                <div className="flex-1 p-4 flex overflow-hidden gap-4">
-                  <div className="flex-1 flex bg-bg-card rounded-2xl shadow-sm border border-border-primary overflow-hidden relative">
-                    <LeftPanel activeTab="chats" />
-                    <ChatPanel />
-                  </div>
+                <div className="flex-1 flex overflow-hidden">
+                  <LeftPanel activeTab="chats" />
+                  <ChatPanel />
                 </div>
               )}
 
@@ -101,22 +96,22 @@ function WorkflowShell() {
 
   if (selectedWorkflow === 'new') {
     return (
-      <>
+      <div className="flex-1 flex overflow-hidden">
         <LeftPanel activeTab="workflows" />
         <NewWorkflowDialog
           onClose={() => setSelectedWorkflow(null)}
           onSuccess={(traceId: string) => setSelectedWorkflow(traceId)}
         />
-      </>
+      </div>
     );
   }
 
   if (selectedWorkflow) {
     return (
-      <>
+      <div className="flex-1 flex overflow-hidden">
         <LeftPanel activeTab="workflows" />
         <RightPanel selectedWorkflow={selectedWorkflow} />
-      </>
+      </div>
     );
   }