feat(finalmask): sync transport with upstream Xray core changes

Consolidate the eight legacy mKCP/header UDP mask types into a single mkcp-legacy type ({header, value}), simplify xicmp to {dgram, ips}, and add the new realm UDP mask type, matching the updated Xray-core wire format. Update the FinalMask schema enum, the transport form, the mKCP seeding default, and the backend KCP share-link translation. Refresh golden fixtures/snapshots and add backend coverage for the mapping.

frontend/src/test/__snapshots__/finalmask.test.ts.snap

@@ -27,7 +27,11 @@ exports[`FinalMaskStreamSettingsSchema fixtures > parses combined byte-stably 1`
       "type": "salamander",
     },
     {
-      "type": "header-wireguard",
+      "settings": {
+        "header": "wireguard",
+        "value": "",
+      },
+      "type": "mkcp-legacy",
     },
   ],
 }
@@ -117,18 +121,24 @@ exports[`FinalMaskStreamSettingsSchema fixtures > parses udp-mask byte-stably 1`
     },
     {
       "settings": {
-        "password": "abcdef0123456789",
+        "header": "",
+        "value": "abcdef0123456789",
       },
-      "type": "mkcp-aes128gcm",
+      "type": "mkcp-legacy",
     },
     {
       "settings": {
-        "domain": "cloudflare.com",
+        "header": "dns",
+        "value": "cloudflare.com",
       },
-      "type": "header-dns",
+      "type": "mkcp-legacy",
     },
     {
-      "type": "header-wireguard",
+      "settings": {
+        "header": "wireguard",
+        "value": "",
+      },
+      "type": "mkcp-legacy",
     },
     {
       "settings": {
@@ -164,11 +174,21 @@ exports[`FinalMaskStreamSettingsSchema fixtures > parses udp-mask byte-stably 1`
     },
     {
       "settings": {
-        "id": 0,
-        "listenIp": "0.0.0.0",
+        "dgram": false,
+        "ips": [],
       },
       "type": "xicmp",
     },
+    {
+      "settings": {
+        "stunServers": [
+          "stun.l.google.com:19302",
+          "global.stun.twilio.com:3478",
+        ],
+        "url": "realm://public@example.com/my-realm",
+      },
+      "type": "realm",
+    },
   ],
 }
 `;

frontend/src/test/golden/fixtures/finalmask/combined.json

@@ -4,7 +4,7 @@
   ],
   "udp": [
     { "type": "salamander", "settings": { "password": "swordfish" } },
-    { "type": "header-wireguard" }
+    { "type": "mkcp-legacy", "settings": { "header": "wireguard", "value": "" } }
   ],
   "quicParams": {
     "congestion": "brutal",

frontend/src/test/golden/fixtures/finalmask/udp-mask.json

@@ -1,9 +1,9 @@
 {
   "udp": [
     { "type": "salamander", "settings": { "password": "swordfish" } },
-    { "type": "mkcp-aes128gcm", "settings": { "password": "abcdef0123456789" } },
-    { "type": "header-dns", "settings": { "domain": "cloudflare.com" } },
-    { "type": "header-wireguard" },
+    { "type": "mkcp-legacy", "settings": { "header": "", "value": "abcdef0123456789" } },
+    { "type": "mkcp-legacy", "settings": { "header": "dns", "value": "cloudflare.com" } },
+    { "type": "mkcp-legacy", "settings": { "header": "wireguard", "value": "" } },
     {
       "type": "noise",
       "settings": {
@@ -23,7 +23,14 @@
     },
     {
       "type": "xicmp",
-      "settings": { "listenIp": "0.0.0.0", "id": 0 }
+      "settings": { "dgram": false, "ips": [] }
+    },
+    {
+      "type": "realm",
+      "settings": {
+        "url": "realm://public@example.com/my-realm",
+        "stunServers": ["stun.l.google.com:19302", "global.stun.twilio.com:3478"]
+      }
     }
   ]
 }