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/@smithy/util-endpoints/dist-es/lib/substring.js

@@ -0,0 +1,9 @@
+export const substring = (input, start, stop, reverse) => {
+    if (start >= stop || input.length < stop) {
+        return null;
+    }
+    if (!reverse) {
+        return input.substring(start, stop);
+    }
+    return input.substring(input.length - stop, input.length - start);
+};