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/schemas/protocols/stream/finalmask.ts

@@ -5,7 +5,7 @@ import { z } from 'zod';
 // plus optional QUIC tuning. The `settings` sub-object is polymorphic on
 // `type`; we model the wire-faithful shape with a permissive
 // record-of-unknown for `settings` and leave per-type tightening to
-// Step 6 — there are ~13 UDP mask types plus 3 TCP mask types, each with
+// Step 6 — there are 8 UDP mask types plus 3 TCP mask types, each with
 // distinct setting fields, and modeling them all as discriminated unions
 // here would dwarf the rest of the stream module without buying anything
 // the safety net doesn't already cover.
@@ -21,19 +21,13 @@ export type TcpMask = z.infer<typeof TcpMaskSchema>;
 
 export const UdpMaskTypeSchema = z.enum([
   'salamander',
-  'mkcp-aes128gcm',
-  'mkcp-original',
-  'header-dns',
-  'header-dtls',
-  'header-srtp',
-  'header-utp',
-  'header-wechat',
-  'header-wireguard',
+  'mkcp-legacy',
   'header-custom',
   'xdns',
   'xicmp',
   'noise',
   'sudoku',
+  'realm',
 ]);
 export type UdpMaskType = z.infer<typeof UdpMaskTypeSchema>;