feat(identity): add audioGainBoost user flag

Adds an audio_gain_boost_enabled status column (plus _at/_by audit
fields) to user_status, exposed as user.audioGainBoost and copied onto
sockets as socket.data.hasAudioGainBoost. The flag marks VIPs allowed to
raise their personal horn/TTS/mic gain ceiling past the global admin gain
settings.

Grant/revoke goes through verificationService so socket flags refresh and
an event is published. Resolution is restricted to verified users, so an
unverified visitor sharing a nickname can never be matched.

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

server/src/services/verificationService/index.js

@@ -27,9 +27,11 @@ const {
   setVerified,
   setDeterrence,
   setMuted,
+  setAudioGainBoost,
   listVerifiedUsers,
   listDeterredUsers,
   listMutedUsers,
+  listAudioGainBoostUsers,
   resolveUserBySelector,
   userToLegacyIdentityEntry,
 } = require('../identityService');
@@ -113,10 +115,17 @@ function refreshSocketIdentityFlags(socket) {
     operational chat/audio tools while preserving the flag for normal roles.
   */
   socket.data.isMuted = isAdminRole(role) ? false : mutedByUser;
+  /*
+    Admins already control the global gain settings, so they carry the raised
+    audio ceiling implicitly for the same reason they carry verification: a
+    stored per-user grant should never be what gates an operator's own tools.
+  */
+  socket.data.hasAudioGainBoost = verifiedByRole || Boolean(user.audioGainBoost?.enabled);
   return {
     isVerified: socket.data.isVerified,
     isDeterred: socket.data.isDeterred,
     isMuted: socket.data.isMuted,
+    hasAudioGainBoost: socket.data.hasAudioGainBoost,
     matchedRecordId: user.id,
     reason: socket.data.isVerified ? 'matched' : 'no_match',
     userId: user.id,
@@ -565,6 +574,53 @@ function setUserMute(selector, enabled, actor = null) {
   return userToLegacyIdentityEntry(user);
 }
 
+/*
+  Audio gain boost is a VIP-only grant. resolveUserBySelector's `includeVerified`
+  flag reads as an inclusion toggle but actually relaxes the verified filter, so
+  passing `false` is what restricts the nickname lookup to verified users. That
+  keeps an unverified visitor from being matched by a shared nickname and handed
+  a raised gain ceiling they are not eligible to use.
+*/
+function setUserAudioGainBoost(selector, enabled, actor = null) {
+  const resolved = resolveUserBySelector(selector, { includeVerified: false, includeDeterred: true });
+  if (resolved.error || !resolved.user) {
+    throw new Error(resolved.error === 'ambiguous_nickname'
+      ? 'Nickname matches multiple VIPs.'
+      : 'VIP not found. Only verified users can be granted an audio gain boost.');
+  }
+  if (!resolved.user.verified?.enabled) {
+    throw new Error('Only verified VIPs can be granted an audio gain boost.');
+  }
+
+  const user = setAudioGainBoost(resolved.user.id, {
+    enabled,
+    actor: actor ? String(actor) : null,
+    at: Date.now(),
+  });
+  refreshSocketsForUser(user.id);
+  publishEvent({
+    source: 'moderation',
+    type: enabled ? 'audio.gainBoostGranted' : 'audio.gainBoostRevoked',
+    payload: {
+      userId: user.id,
+      cookieUserId: user.cookieUserIds[0] || null,
+      nickname: user.nickname,
+      actor: actor ? String(actor) : null,
+      ts: Date.now(),
+    },
+  });
+  emitChange(enabled ? 'audio_gain_boost_grant' : 'audio_gain_boost_revoke', { userId: user.id });
+  return userToLegacyIdentityEntry(user);
+}
+
+function grantAudioGainBoost(selector, actor = null) {
+  return setUserAudioGainBoost(selector, true, actor);
+}
+
+function revokeAudioGainBoost(selector, actor = null) {
+  return setUserAudioGainBoost(selector, false, actor);
+}
+
 function muteUser(selector, actor = null) {
   return setUserMute(selector, true, actor);
 }
@@ -696,9 +752,13 @@ module.exports = {
   undeterUser,
   muteUser,
   unmuteUser,
+  listAudioGainBoostUsers,
+  grantAudioGainBoost,
+  revokeAudioGainBoost,
   isVerified: (socket) => Boolean(socket?.data?.isVerified),
   isDeterred: (socket) => Boolean(socket?.data?.isDeterred),
   isMuted: (socket) => Boolean(socket?.data?.isMuted),
+  hasAudioGainBoost: (socket) => Boolean(socket?.data?.hasAudioGainBoost),
   reevaluateSocketVerification,
   reevaluateSocketDeterrence,
   verificationEvents,