feat(mtproto): add domain-fronting and essential mtg options

Expose mtg's [domain-fronting] section (ip/port/proxy-protocol) plus
proxy-protocol-listener, prefer-ip, and debug on MTProto inbounds. Each
key is written to the generated mtg-<id>.toml only when set, so mtg's own
defaults apply otherwise. The instance fingerprint now covers these
fields, so editing an option restarts the sidecar.

Since MTProto is mtg-served (not Xray), sniffing does not apply: hide the
Sniffing tab and the Advanced sniffing sub-editor, drop it from the
Advanced "All" JSON view, and emit empty sniffing in the wire payload,
all gated by a new canEnableSniffing predicate.

web/translation/id-ID.json

@@ -503,7 +503,13 @@
         "encryptionMethod": "Metode enkripsi",
         "fakeTlsDomain": "Domain FakeTLS (SNI)",
         "mtprotoSecret": "Secret",
-        "mtprotoHint": "MTProto dijalankan oleh proses mtg terpisah, bukan Xray. Pengaturan stream dan klien tidak berlaku di sini — bagikan tautan di bawah ke Telegram.",
+        "mtgDomainFrontingIp": "IP domain fronting",
+        "mtgDomainFrontingPort": "Port domain fronting",
+        "mtgDomainFrontingProxyProtocol": "Protokol PROXY domain fronting",
+        "mtgDomainFrontingHint": "Tujuan mtg mengirim lalu lintas non-Telegram — mis. situs palsu NGINX Anda. Kosongkan IP untuk memakai domain FakeTLS melalui DNS; port bawaan adalah 443.",
+        "mtgProxyProtocolListener": "Terima protokol PROXY (listener)",
+        "mtgPreferIp": "Preferensi IP",
+        "mtgDebug": "Log debug",
         "visionTestseed": "Vision testseed",
         "version": "Versi",
         "udpIdleTimeout": "UDP idle timeout (d)",