add API tab to display backend documentation

lightrag_webui/src/App.tsx

@@ -12,6 +12,7 @@ import SiteHeader from '@/features/SiteHeader'
 import GraphViewer from '@/features/GraphViewer'
 import DocumentManager from '@/features/DocumentManager'
 import RetrievalTesting from '@/features/RetrievalTesting'
+import ApiSite from '@/features/ApiSite'
 
 import { Tabs, TabsContent } from '@/components/ui/Tabs'
 
@@ -57,6 +58,9 @@ function App() {
             <TabsContent value="retrieval" className="absolute top-0 right-0 bottom-0 left-0">
               <RetrievalTesting />
             </TabsContent>
+            <TabsContent value="api" className="absolute top-0 right-0 bottom-0 left-0">
+              <ApiSite />
+            </TabsContent>
           </div>
         </Tabs>
         {enableHealthCheck && <StatusIndicator />}