fix(finalmask): hop client UDP through the udphop mask

xray-core 26.9.9 dropped finalmask.quicParams.udpHop for the client-only
"udphop" UDP mask {mode, interval, remoteIPs, remotePorts}. The panel kept
writing the old key, so hysteria/xhttp outbounds and JSON-subscription
clients silently stopped hopping ports.

An inbound keeps quicParams.udpHop: it is panel metadata advertised as the
link's mport, and a udphop mask on a listener fails with "udphop: client
only". The conversion (maskcompat.UpgradeLegacyUDPHop, intervalRemote mode)
runs only where a client config is produced:

- UDPHopClientMaskFix seeder over hosts, sub-JSON finalmask, cached
  outbound-subscription outbounds and template outbounds (never inbounds);
- GetXrayConfig heals template outbounds at build time;
- the JSON subscription upgrades each generated client stream;
- the Go and frontend link importers upgrade a legacy fm= param.

The finalmask editor gains a side prop: the client side lifts the dead key
on mount and offers a udphop mask editor (also for xhttp's HTTP/3 dial);
the inbound side keeps the UDP Hop switch, labelled as advertised.

internal/util/link/outbound.go

@@ -769,6 +769,7 @@ func applyFinalMask(stream map[string]any, p url.Values) {
 		if json.Unmarshal([]byte(fm), &parsed) == nil {
 			sanitizeFinalMaskQuicParams(parsed)
 			maskcompat.UpgradeLegacyXdns(parsed)
+			maskcompat.UpgradeLegacyUDPHop(parsed)
 			stream["finalmask"] = parsed
 		}
 	}