feat(xray): add loopback sniffing and per-segment fragment masks

- Loopback outbound: add sniffing support (xray-core #6320)

- FinalMask fragment: support per-segment lengths/delays arrays with legacy length/delay migration (xray-core #6334)

- Consolidate sniffing into a shared SniffingFields component and the canonical SniffingSchema across inbound, VLESS reverse, and loopback

frontend/src/lib/xray/forms/SniffingFields.tsx

@@ -0,0 +1,63 @@
+import { useTranslation } from 'react-i18next';
+import { Form, Select, Switch } from 'antd';
+import type { FormInstance } from 'antd/es/form';
+
+import { SNIFFING_OPTION } from '@/schemas/primitives';
+
+const DEST_OPTIONS = Object.entries(SNIFFING_OPTION).map(([label, value]) => ({ value, label }));
+
+export interface SniffingFieldsProps {
+  // Base path to the sniffing object in the form, e.g. ['sniffing'] (inbound),
+  // ['settings', 'reverseSniffing'] (VLESS reverse), ['settings', 'sniffing']
+  // (loopback). All sub-fields hang off this path.
+  name: (string | number)[];
+  form: FormInstance;
+  // Label for the enable toggle — Enable / Reverse Sniffing / Sniffing differ
+  // per host.
+  enableLabel: string;
+}
+
+// Shared sniffing form fragment used everywhere the panel edits an xray
+// SniffingConfig: the inbound Sniffing tab, VLESS reverse sniffing, and the
+// loopback outbound. Renders the enable toggle plus the destOverride /
+// metadataOnly / routeOnly / excluded fields when enabled.
+export default function SniffingFields({ name, form, enableLabel }: SniffingFieldsProps) {
+  const { t } = useTranslation();
+  const enabled = Form.useWatch([...name, 'enabled'], form) ?? false;
+
+  return (
+    <>
+      <Form.Item label={enableLabel} name={[...name, 'enabled']} valuePropName="checked">
+        <Switch />
+      </Form.Item>
+
+      {enabled && (
+        <>
+          <Form.Item name={[...name, 'destOverride']} wrapperCol={{ md: { span: 14, offset: 8 } }}>
+            <Select mode="multiple" className="sniffing-options" options={DEST_OPTIONS} />
+          </Form.Item>
+          <Form.Item
+            label={t('pages.inbounds.sniffingMetadataOnly')}
+            name={[...name, 'metadataOnly']}
+            valuePropName="checked"
+          >
+            <Switch />
+          </Form.Item>
+          <Form.Item
+            label={t('pages.inbounds.sniffingRouteOnly')}
+            name={[...name, 'routeOnly']}
+            valuePropName="checked"
+          >
+            <Switch />
+          </Form.Item>
+          <Form.Item label={t('pages.inbounds.sniffingIpsExcluded')} name={[...name, 'ipsExcluded']}>
+            <Select mode="tags" tokenSeparators={[',']} placeholder="IP/CIDR/geoip:*/ext:*" style={{ width: '100%' }} />
+          </Form.Item>
+          <Form.Item label={t('pages.inbounds.sniffingDomainsExcluded')} name={[...name, 'domainsExcluded']}>
+            <Select mode="tags" tokenSeparators={[',']} placeholder="domain:*/ext:*" style={{ width: '100%' }} />
+          </Form.Item>
+        </>
+      )}
+    </>
+  );
+}