Move auth and timezone hooks into dedicated hook files

frontend/src/pages/LoginPage.tsx

@@ -21,7 +21,7 @@ import {
 import { useNavigate, useSearchParams } from "react-router-dom";
 import type { ChangeEvent, FormEvent } from "react";
 import { ApiError } from "../api/client";
-import { useAuth } from "../providers/AuthProvider";
+import { useAuth } from "../hooks/useAuth";
 
 // ---------------------------------------------------------------------------
 // Styles