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/modals/inbound_info_modal.html

@@ -90,14 +90,9 @@
       <a-tag :color="inbound.stream.security == 'none' ? 'red' : 'green'">[[
         inbound.stream.security ]]</a-tag>
       <br />
-      <td>Authentication</td>
-      <a-tag v-if="inbound.settings.selectedAuth" color="green">[[
-        inbound.settings.selectedAuth ? inbound.settings.selectedAuth : ''
-        ]]</a-tag>
-      <a-tag v-else color="red">{{ i18n "none" }}</a-tag>
-      <br />
       {{ i18n "encryption" }}
-      <a-tag class="info-large-tag" :color="inbound.settings.encryption ? 'green' : 'red'">[[
+      <a-tag class="info-large-tag"
+        :color="inbound.settings.encryption && inbound.settings.encryption !== 'none' ? 'green' : 'red'">[[
         inbound.settings.encryption ? inbound.settings.encryption : ''
         ]]</a-tag>
       <a-tooltip title='{{ i18n "copy" }}'>