Fix file and backup downloading to use URL returned by server

resources/scripts/api/server/backups/getBackupDownloadUrl.ts

@@ -0,0 +1,9 @@
+import http from '@/api/http';
+
+export default (uuid: string, backup: string): Promise<string> => {
+    return new Promise((resolve, reject) => {
+        http.get(`/api/client/servers/${uuid}/backups/${backup}/download`)
+            .then(({ data }) => resolve(data.attributes.url))
+            .catch(reject);
+    });
+};