Disable touch drag & drop, warn on car delete with reservations, configure backend URL

Co-authored-by: pdf114514 <57948770+pdf114514@users.noreply.github.com>
Agent-Logs-Url: https://github.com/pdf114514/CarReservation/sessions/cd194ca1-b339-4f2f-b717-31a0ba193964

frontend/src/api.js

@@ -1,4 +1,4 @@
-const API_BASE = '/api';
+const API_BASE = (import.meta.env.VITE_API_BASE_URL ?? '') + '/api';
 
 async function request(path, options = {}) {
   const res = await fetch(`${API_BASE}${path}`, {