Fixed .env file name

frontend/src/views/Login.vue

@@ -24,7 +24,7 @@ export default {
     ...mapActions(['login']),
     async executeLogin() {
       try {
-        const response = await axios.post(`${process.env.BACKEND}/api/auth/login`, { email: this.email, password: this.password }, {
+        const response = await axios.post(`${process.env.VUE_APP_BACKEND}/api/auth/login`, { email: this.email, password: this.password }, {
           timeout: 5000, 
         });
         await this.login({ token: response.data.token, username: this.email });