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/append-field/index.js

@@ -0,0 +1,12 @@
+var parsePath = require('./lib/parse-path')
+var setValue = require('./lib/set-value')
+
+function appendField (store, key, value) {
+  var steps = parsePath(key)
+
+  steps.reduce(function (context, step) {
+    return setValue(context, step, context[step.key], value)
+  }, store)
+}
+
+module.exports = appendField