feat(finalmask): support Salamander packetSize (Gecko) and Realm tlsConfig for Hysteria2 (#5278)

* feat(finalmask): support salamander packetSize (Gecko) and realm tlsConfig

Hysteria v2.9.1/v2.9.2 added two finalmask features that the pinned
Xray-core (26.6.1, 94ffd50) already supports but the panel UI did not
expose: Salamander's packetSize range (Gecko, XTLS/Xray-core#6198) and
the Realm UDP hole-punching mask's optional tlsConfig (XTLS/Xray-core#6137).

Add typed schemas and form fields for both, keeping UdpMaskSchema.settings
permissive per the existing finalmask design note. packetSize reuses the
existing dash-range preprocess (like udpHop.ports) so it round-trips under
the fm= share-link param with no new URI key; realm tlsConfig emits xray's
flat TLSConfig shape (serverName/alpn/fingerprint/allowInsecure).

Verified against the bundled Xray 26.6.1: configs with packetSize and
realm tlsConfig validate (Configuration OK.), plain salamander stays
backward-compatible, and a malformed packetSize is correctly rejected by
the salamander mask builder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(finalmask): add snapshots for salamander-gecko and realm-tls fixtures

vitest run does not auto-create missing snapshots in CI mode, so the two
new fixtures need committed snapshot entries. Verified under node:22 that
finalmask.test.ts passes (6/6) with these snapshots.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(finalmask): polished Gecko UX with core-grounded validation

Fold PR #5281's Gecko work into the Realm tlsConfig base:

- Replace the plain packetSize input with a Salamander/Gecko mode
  selector and validated Min/Max number inputs.
- parseGeckoPacketSize enforces xray-core's real bound
  (1 <= min <= max <= 2048, the gecko buffer size) so the panel
  rejects configs core would reject at runtime.
- Accurate Gecko description; add parser unit tests.
- Drop the unused Salamander/Realm settings schemas; settings stay
  permissive and are validated at the form level.

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>

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

@@ -61,6 +61,46 @@ exports[`FinalMaskStreamSettingsSchema fixtures > parses quic-params byte-stably
 }
 `;
 
+exports[`FinalMaskStreamSettingsSchema fixtures > parses realm-tls byte-stably 1`] = `
+{
+  "tcp": [],
+  "udp": [
+    {
+      "settings": {
+        "stunServers": [
+          "stun.l.google.com:19302",
+        ],
+        "tlsConfig": {
+          "allowInsecure": false,
+          "alpn": [
+            "h3",
+          ],
+          "fingerprint": "chrome",
+          "serverName": "example.com",
+        },
+        "url": "realm://public@example.com/my-realm",
+      },
+      "type": "realm",
+    },
+  ],
+}
+`;
+
+exports[`FinalMaskStreamSettingsSchema fixtures > parses salamander-gecko byte-stably 1`] = `
+{
+  "tcp": [],
+  "udp": [
+    {
+      "settings": {
+        "packetSize": "100-200",
+        "password": "swordfish",
+      },
+      "type": "salamander",
+    },
+  ],
+}
+`;
+
 exports[`FinalMaskStreamSettingsSchema fixtures > parses tcp-mask byte-stably 1`] = `
 {
   "tcp": [