Fix overflow issues in UI components

- Set overflow-hidden for main container
- Add overflow-auto to documents tab
- Add overflow-hidden to graph and retrieval tabs
- Set overflow-hidden for SigmaContainer
- Set overflow-hidden for retrieval testing container

lightrag_webui/src/features/RetrievalTesting.tsx

@@ -112,7 +112,7 @@ export default function RetrievalTesting() {
   }, [setMessages])
 
   return (
-    <div className="flex size-full gap-2 px-2 pb-12">
+    <div className="flex size-full gap-2 px-2 pb-12 overflow-hidden">
       <div className="flex grow flex-col gap-4">
         <div className="relative grow">
           <div className="bg-primary-foreground/60 absolute inset-0 flex flex-col overflow-auto rounded-lg border p-2">