fix: fix yarn dev not working due to const variable re-assignment

It was causing this error

  ✘ [ERROR] Cannot assign to "isLoggedIn" because it is a constant

    src/router.js:230:2:
      230 │     isLoggedIn = false
          ╵     ~~~~~~~~~~

  The symbol "isLoggedIn" was declared a constant here:

    src/router.js:222:7:
      222 │   const { isLoggedIn } = sessionStore()
          ╵         ^

frontend/src/router.js

@@ -219,7 +219,7 @@ let router = createRouter({
 
 router.beforeEach(async (to, from, next) => {
 	const { userResource } = usersStore()
-	const { isLoggedIn } = sessionStore()
+	let { isLoggedIn } = sessionStore()
 	const { allowGuestAccess } = useSettings()
 
 	try {