Remove dead/stale code, dedup close+escalation paths

Dead/stale removals (grep-confirmed no consumers):
- config: drop 9 unread CONFIG keys (ROLE_TO_PING_ID, SIGNATURE,
  REMINDER_*, RENAME_LOG_CHANNEL_ID, SETTINGS_*); remove their
  ALLOWED_CONFIG_KEYS entries and the orphaned settings-site UI fields
- configSchema: delete unreachable json/string_or_json validators
- models: drop unused ticketTag field
- gmail-poll: remove unused isPollSuspended export
- utils: remove dead htmlToTextWithBlocks/decodeHtmlEntities/BLOCK_TAG_REGEX
- internalApi: remove router._allowedKeys (test it served is gone)
- discord client: drop unused GuildPresences privileged intent
- broccolini-discord: remove dormant /api 503 gate (no /api routes)

Fixes:
- context-menu ticket create now uses makeTicketName('unclaimed', ...)
  instead of the contract-violating ticket-<n> name
- drop write-only pending.userId from both close paths

Dedup / simplify:
- new services/transcript.js shares the transcript text/date/header
  builders between the button and force-close paths (had drifted)
- resolveEscalationCategoryId() replaces 3 copies of the category logic
- ticketChannelOverwrites() shares the create-permission array between
  the two interactive ticket-create paths
- finalizeBody() shares the email-cleanup tail in parseGmailMessage
- getTicketActionRow drops its never-passed options arg;
  sendTicketNotificationEmail drops its always-null subjectLine arg
- hoist invariant guild lookup out of the auto-close/unclaim loops
- drop redundant lastActivity write (and now-dead updateTicketActivity)
- /help lists all current commands and the right-click apps

services/gmail.js

@@ -182,18 +182,17 @@ async function sendTicketClosedEmail(ticket, closerName, userId = null) {
 /**
  * Send a notification email in the ticket thread (e.g. escalation, high-priority).
  * @param {Object} ticket - Ticket with gmailThreadId, senderEmail, subject
- * @param {string} subjectLine - Fallback subject if the thread can't be queried
  * @param {string} messageBody - Plain or HTML message body
  * @param {string} [userId] - Discord user ID for signature (optional)
  */
-async function sendTicketNotificationEmail(ticket, subjectLine, messageBody, userId = null) {
+async function sendTicketNotificationEmail(ticket, messageBody, userId = null) {
   try {
     const recipient = resolveCustomerRecipient(ticket, 'sendTicketNotificationEmail');
     if (!recipient) return;
 
     const gmail = getGmailClient();
     const { subject, msgId } = await fetchThreadSubjectAndMsgId(gmail, ticket.gmailThreadId);
-    const encodedSubject = encodeReplySubject(subject || subjectLine || ticket.subject || 'Support');
+    const encodedSubject = encodeReplySubject(subject || ticket.subject || 'Support');
 
     await sendThreadedEmail(gmail, {
       threadId: ticket.gmailThreadId,