fix: 修复配额说明重复和undefined问题

- 在editStorageForm中初始化oss_storage_quota_value和oss_quota_unit
- 删除重复的旧配额说明块，保留新的当前配额设置显示

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/node_modules/lodash/isNull.js

@@ -0,0 +1,22 @@
+/**
+ * Checks if `value` is `null`.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is `null`, else `false`.
+ * @example
+ *
+ * _.isNull(null);
+ * // => true
+ *
+ * _.isNull(void 0);
+ * // => false
+ */
+function isNull(value) {
+  return value === null;
+}
+
+module.exports = isNull;