fix(inbound): strip XHTTP client-only fields from xray config, keep for subscriptions (#5349)

Inbound XMUX and other client-side xHTTP knobs were written into
bin/config.json even though xray-core's server listener ignores them.
Strip them in GenXrayInboundConfig while leaving the DB row intact so
buildXhttpExtra still pushes defaults to clients via share links.

frontend/src/test/stream-wire-normalize.test.ts

@@ -66,7 +66,7 @@ describe('normalizeXhttpForWire stream-one', () => {
     expect(out).not.toHaveProperty('scMaxEachPostBytes');
   });
 
-  it('keeps inbound xmux when enableXmux is on (for the share-link extra)', () => {
+  it('keeps inbound xmux when enableXmux is on (stored for subscription extra; stripped from xray config on Go side)', () => {
     const out = normalizeXhttpForWire({
       path: '/app',
       mode: 'auto',