fix(inbounds): restore xHTTP Headers editor in form

The xHTTP transport schema and share-link emitter already supported a
headers map, but the inbound form lost its editor row, so operators had
no way to set custom headers on xHTTP inbounds. Add the HeaderMapEditor
row in the same position the outbound form uses.

frontend/src/pages/inbounds/InboundFormModal.tsx

@@ -1982,6 +1982,12 @@ export default function InboundFormModal({
           >
             <Input />
           </Form.Item>
+          <Form.Item
+            name={['streamSettings', 'xhttpSettings', 'headers']}
+            label={t('pages.inbounds.form.headers')}
+          >
+            <HeaderMapEditor mode="v1" />
+          </Form.Item>
           <Form.Item
             name={['streamSettings', 'xhttpSettings', 'uplinkHTTPMethod']}
             label={t('pages.inbounds.form.uplinkHttpMethod')}