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/multer/storage/memory.js

@@ -0,0 +1,21 @@
+var concat = require('concat-stream')
+
+function MemoryStorage (opts) {}
+
+MemoryStorage.prototype._handleFile = function _handleFile (req, file, cb) {
+  file.stream.pipe(concat({ encoding: 'buffer' }, function (data) {
+    cb(null, {
+      buffer: data,
+      size: data.length
+    })
+  }))
+}
+
+MemoryStorage.prototype._removeFile = function _removeFile (req, file, cb) {
+  delete file.buffer
+  cb(null)
+}
+
+module.exports = function (opts) {
+  return new MemoryStorage(opts)
+}