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/simple-concat/index.js

@@ -0,0 +1,15 @@
+/*! simple-concat. MIT License. Feross Aboukhadijeh <https://feross.org/opensource> */
+module.exports = function (stream, cb) {
+  var chunks = []
+  stream.on('data', function (chunk) {
+    chunks.push(chunk)
+  })
+  stream.once('end', function () {
+    if (cb) cb(null, Buffer.concat(chunks))
+    cb = null
+  })
+  stream.once('error', function (err) {
+    if (cb) cb(err)
+    cb = null
+  })
+}