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/text-decoder/lib/pass-through-decoder.js

@@ -0,0 +1,19 @@
+const b4a = require('b4a')
+
+module.exports = class PassThroughDecoder {
+  constructor (encoding) {
+    this.encoding = encoding
+  }
+
+  get remaining () {
+    return 0
+  }
+
+  decode (tail) {
+    return b4a.toString(tail, this.encoding)
+  }
+
+  flush () {
+    return ''
+  }
+}