Use UTF-8 safe return-to encoding and decoding across router and login

Co-Authored-By: Codex <codex@openai.com>

src/stores/login.ts

@@ -13,6 +13,7 @@ import { defineStore } from "pinia";
 import axios from "axios";
 import apiClient from "@/api/client.js";
 import apiError from "@/module/apiError.js";
+import { decodeReturnTo } from "@/utils/returnToEncoding";
 import {
   deleteCookie,
   setCookie,
@@ -73,7 +74,7 @@ export const useLoginStore = defineStore("loginStore", {
         if (this.rememberedReturnToUrl !== "") {
           let decodedUrl = "";
           try {
-            decodedUrl = atob(this.rememberedReturnToUrl);
+            decodedUrl = decodeReturnTo(this.rememberedReturnToUrl);
           } catch {
             this.$router.push("/files");
             return;