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/assets/js/model/inbound.js

@@ -2543,7 +2543,6 @@ Inbound.VLESSSettings = class extends Inbound.Settings {
         decryption = "none",
         encryption = "none",
         fallbacks = [],
-        selectedAuth = undefined,
         testseed = [],
     ) {
         super(protocol);
@@ -2551,7 +2550,6 @@ Inbound.VLESSSettings = class extends Inbound.Settings {
         this.decryption = decryption;
         this.encryption = encryption;
         this.fallbacks = fallbacks;
-        this.selectedAuth = selectedAuth;
         this.testseed = testseed;
     }
 
@@ -2587,7 +2585,6 @@ Inbound.VLESSSettings = class extends Inbound.Settings {
             json.decryption,
             json.encryption,
             Inbound.VLESSSettings.Fallback.fromJson(json.fallbacks || []),
-            json.selectedAuth,
             testseed,
         );
         return obj;
@@ -2610,9 +2607,6 @@ Inbound.VLESSSettings = class extends Inbound.Settings {
         if (this.fallbacks && this.fallbacks.length > 0) {
             json.fallbacks = Inbound.VLESSSettings.toJsonArray(this.fallbacks);
         }
-        if (this.selectedAuth) {
-            json.selectedAuth = this.selectedAuth;
-        }
 
         // testseed is only meaningful for the exact xtls-rprx-vision flow, and only when
         // the user supplied a complete 4-positive-int array. Otherwise omit and let the