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/b4a/lib/ascii.js

@@ -0,0 +1,31 @@
+function byteLength(string) {
+  return string.length
+}
+
+function toString(buffer) {
+  const len = buffer.byteLength
+
+  let result = ''
+
+  for (let i = 0; i < len; i++) {
+    result += String.fromCharCode(buffer[i])
+  }
+
+  return result
+}
+
+function write(buffer, string) {
+  const len = buffer.byteLength
+
+  for (let i = 0; i < len; i++) {
+    buffer[i] = string.charCodeAt(i)
+  }
+
+  return len
+}
+
+module.exports = {
+  byteLength,
+  toString,
+  write
+}