fix(outbound): preserve custom headers for HTTP outbounds (#5519)

The Outbounds form routed HTTP through the SOCKS-shared simpleAuth adapter, which only knew address/port/user/pass, so xray's top-level settings.headers was dropped on both load and save. Opening and re-saving an HTTP outbound destroyed its headers.

Add headers to the HTTP wire/form schemas, round-trip it via dedicated httpFromWire/httpToWire helpers, and expose a HeaderMapEditor in the form. Only settings-level headers round-trip; xray-core ignores per-server headers.

frontend/src/pages/xray/outbounds/protocols/http.tsx

@@ -1,6 +1,8 @@
 import { useTranslation } from 'react-i18next';
 import { Form, Input } from 'antd';
 
+import { HeaderMapEditor } from '@/components/form';
+
 export default function HttpFields() {
   const { t } = useTranslation();
   return (
@@ -11,6 +13,9 @@ export default function HttpFields() {
       <Form.Item label={t('password')} name={['settings', 'pass']}>
         <Input />
       </Form.Item>
+      <Form.Item label={t('pages.inbounds.form.headers')} name={['settings', 'headers']}>
+        <HeaderMapEditor mode="v1" />
+      </Form.Item>
     </>
   );
 }