fix(nav): fix exam flow navigation

chore(zustand): refactor auth code for zustand store

app/exam/pretest/page.tsx

@@ -13,7 +13,6 @@ import {
 import DestructibleAlert from "@/components/DestructibleAlert";
 import BackgroundWrapper from "@/components/BackgroundWrapper";
 import { API_URL, getToken } from "@/lib/auth";
-import { Test } from "@/types/exam";
 import { Metadata } from "@/types/exam";
 import { useExamStore } from "@/stores/examStore";
 
@@ -21,15 +20,9 @@ function PretestPageContent() {
   const router = useRouter();
   const searchParams = useSearchParams();
 
-  const [examData, setExamData] = useState<Test>();
-
   // Get params from URL search params
   const id = searchParams.get("test_id") || "";
-  const typeParam = searchParams.get("type");
-  const type =
-    typeParam === "mock" || typeParam === "subject" || typeParam === "topic"
-      ? typeParam
-      : null;
+  const type = searchParams.get("type");
 
   const [metadata, setMetadata] = useState<Metadata | null>(null);
   const [loading, setLoading] = useState(true);
@@ -56,10 +49,8 @@ function PretestPageContent() {
 
         const data = await questionResponse.json();
         const fetchedMetadata: Metadata = data.metadata;
-        const fetchedQuestions: Test = data.questions;
 
         setMetadata(fetchedMetadata);
-        setExamData(fetchedQuestions);
       } catch (error) {
         console.error(error);
         setError(error instanceof Error ? error.message : "An error occurred");
@@ -122,7 +113,7 @@ function PretestPageContent() {
   }
 
   function handleStartExam() {
-    if (!examData) return;
+    if (!metadata) return;
     setStatus("in-progress");
 
     router.push(
@@ -135,7 +126,7 @@ function PretestPageContent() {
         <div className="flex-1 overflow-y-auto mb-20">
           {metadata ? (
             <div className="mx-10 mt-10 gap-6 pb-6 space-y-6">
-              <button onClick={() => router.back()}>
+              <button onClick={() => router.replace(`/categories/${type}s`)}>
                 <ArrowLeft size={30} color="black" />
               </button>