refactor(vless): drop selectedAuth, expose two explicit auth buttons

selectedAuth was UI-only metadata (Xray never reads it) and entirely
redundant with the encryption string itself — the dropdown only
controlled which block from `xray vlessenc` to apply. Replace it with
two explicit buttons ("X25519" and "ML-KEM-768") so the user picks
the auth mode in one click instead of dropdown + Get-New-Keys.

- VLESSSettings drops the field from constructor, fromJson, and toJson;
  legacy `selectedAuth` values still in DB will be silently shed on the
  next save.
- getNewVlessEnc(authLabel) now takes the label as a parameter; clear
  resets only decryption/encryption.
- Fallbacks visibility now keys on encryption === "none" (the same
  thing the dropdown was effectively gating on).
- Info modal drops the redundant Authentication tag and colours the
  encryption tag red when it's "none", green otherwise.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/html/form/protocol/vless.html

@@ -21,16 +21,6 @@
 </a-collapse>
 <template v-if=" !inbound.stream.isTLS || !inbound.stream.isReality">
   <a-form :colon="false" :label-col="{ md: {span:8} }" :wrapper-col="{ md: {span:14} }">
-    <a-form-item label="Authentication">
-      <a-select v-model="inbound.settings.selectedAuth" @change="getNewVlessEnc"
-        :dropdown-class-name="themeSwitcher.currentTheme">
-        <a-select-option :value="undefined">None</a-select-option>
-        <a-select-option value="X25519, not Post-Quantum">X25519 (not
-          Post-Quantum)</a-select-option>
-        <a-select-option value="ML-KEM-768, Post-Quantum">ML-KEM-768
-          (Post-Quantum)</a-select-option>
-      </a-select>
-    </a-form-item>
     <a-form-item label="decryption">
       <a-input v-model.trim="inbound.settings.decryption"></a-input>
     </a-form-item>
@@ -38,16 +28,20 @@
       <a-input v-model="inbound.settings.encryption"></a-input>
     </a-form-item>
     <a-form-item label=" ">
-      <a-space>
-        <a-button type="primary" icon="import" @click="getNewVlessEnc">Get New
-          keys</a-button>
+      <a-space :size="8" wrap>
+        <a-button type="primary" icon="import" @click="getNewVlessEnc('X25519, not Post-Quantum')">
+          X25519
+        </a-button>
+        <a-button type="primary" icon="import" @click="getNewVlessEnc('ML-KEM-768, Post-Quantum')">
+          ML-KEM-768
+        </a-button>
         <a-button danger @click="clearVlessEnc">Clear</a-button>
       </a-space>
     </a-form-item>
   </a-form>
   <a-divider :style="{ margin: '5px 0' }"></a-divider>
 </template>
-<template v-if="inbound.isTcp && !inbound.settings.selectedAuth">
+<template v-if="inbound.isTcp && (!inbound.settings.encryption || inbound.settings.encryption === 'none')">
   <a-form :colon="false" :label-col="{ md: {span:8} }" :wrapper-col="{ md: {span:14} }">
     <a-form-item label="Fallbacks">
       <a-button icon="plus" type="primary" size="small" @click="inbound.settings.addFallback()"></a-button>