refactor: centralize authentication handling

- Replaced direct localStorage token access with a centralized `getBearerToken` function across various components and hooks to improve code maintainability and security.
- Updated API calls to use `authenticatedFetch` for consistent authentication handling.
- Enhanced user experience by ensuring proper redirection to login when authentication fails.
- Cleaned up unused imports and improved overall code structure for better readability.

surfsense_web/hooks/use-chat.ts

@@ -3,6 +3,7 @@ import { useCallback, useEffect, useState } from "react";
 import type { ChatDetails } from "@/app/dashboard/[search_space_id]/chats/chats-client";
 import type { ResearchMode } from "@/components/chat";
 import type { Document } from "@/hooks/use-documents";
+import { getBearerToken } from "@/lib/auth-utils";
 
 interface UseChatStateProps {
 	search_space_id: string;
@@ -22,7 +23,7 @@ export function useChatState({ chat_id }: UseChatStateProps) {
 	const [topK, setTopK] = useState<number>(5);
 
 	useEffect(() => {
-		const bearerToken = localStorage.getItem("surfsense_bearer_token");
+		const bearerToken = getBearerToken();
 		setToken(bearerToken);
 	}, []);