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/base64-js/index.d.ts

@@ -0,0 +1,3 @@
+export function byteLength(b64: string): number;
+export function toByteArray(b64: string): Uint8Array;
+export function fromByteArray(uint8: Uint8Array): string;