Email ticketing fixes, comms polish, and .env cleanup

Inbound:
- Gmail poll query is:unread in:inbox (was category:primary, which matched
  nothing on a no-tabs Workspace inbox)

Outbound email:
- Closed/escalation auto-emails editable via TICKET_CLOSE_MESSAGE and new
  TICKET_ESCALATION_EMAIL_MESSAGE; drop the staff signature from closing emails
- Replies quote the customer's latest message (gmail_quote markup so clients
  collapse it), embed custom emoji inline via CID attachment, and strip Discord
  role mentions
- Tagline spacing fix in the company signature

Discord side:
- Suppress all mentions in log + transcript posts (no more pinging on close)
- Drop the staff-role ping from new-ticket and follow-up notifications
- Ticket channels inherit category permissions instead of setting per-channel
  overwrites (removes the Manage Roles requirement)

Gmail folders:
- Folder/label routing (gmailLabels.js) with /folder; close files to Complete

Config:
- Remove ~56 stale .env keys for long-removed features; refresh stale copy

Docs:
- Design specs for folder routing, email-flow toggle, and per-staff metrics

services/configSchema.js

@@ -35,17 +35,17 @@ const ALLOWED_CONFIG_KEYS = new Set([
   'BUTTON_LABEL_CLOSE', 'BUTTON_LABEL_CLAIM', 'BUTTON_LABEL_UNCLAIM',
   'BUTTON_EMOJI_CLOSE', 'BUTTON_EMOJI_CLAIM', 'BUTTON_EMOJI_UNCLAIM',
   // Branding
-  'LOGO_URL', 'SUPPORT_NAME', 'EMAIL_SIGNATURE', 'GAME_LIST',
+  'LOGO_URL', 'SUPPORT_NAME', 'GAME_LIST',
   // Toggles
   'AUTO_CLOSE_ENABLED', 'AUTO_CLOSE_AFTER_HOURS', 'AUTO_UNCLAIM_ENABLED', 'AUTO_UNCLAIM_AFTER_HOURS',
-  'ALLOW_CLAIM_OVERWRITE',
+  'ALLOW_CLAIM_OVERWRITE', 'TRANSCRIPT_DM_TO_CREATOR',
   'PRIORITY_ENABLED', 'DEFAULT_PRIORITY',
   'STAFF_THREAD_ENABLED', 'STAFF_THREAD_NAME', 'STAFF_THREAD_AUTO_ADD_ROLE', 'STAFF_THREAD_ROLE_ID',
   'PIN_INITIAL_MESSAGE_ENABLED', 'PIN_ESCALATION_MESSAGE_ENABLED', 'PIN_SUPPRESS_SYSTEM_MESSAGE',
   // Limits and thresholds
   'GLOBAL_TICKET_LIMIT',
   'RATE_LIMIT_TICKETS_PER_USER', 'RATE_LIMIT_WINDOW_MINUTES',
-  'FORCE_CLOSE_TIMER_SECONDS', 'GMAIL_POLL_INTERVAL_SECONDS',
+  'FORCE_CLOSE_TIMER_SECONDS', 'GMAIL_POLL_INTERVAL_SECONDS', 'GMAIL_POLL_ENABLED',
   // Embed colors
   'EMBED_COLOR_OPEN', 'EMBED_COLOR_CLAIMED', 'EMBED_COLOR_ESCALATED', 'EMBED_COLOR_INFO',
   'PRIORITY_HIGH_EMOJI', 'PRIORITY_MEDIUM_EMOJI', 'PRIORITY_LOW_EMOJI'
@@ -163,6 +163,8 @@ function inferType(key) {
   if (key.includes('COLOR')) return 'hex_color';
   // ROLE_ID_TO_PING has _ID mid-key — standard _ID$ pattern misses it.
   if (key === 'ROLE_ID_TO_PING') return 'discord_id';
+  // Boolean toggle whose name doesn't match the ENABLED/_ON pattern.
+  if (key === 'TRANSCRIPT_DM_TO_CREATOR') return 'boolean';
 
   // 2. Name patterns
   if (/ENABLED$|^USE_|_ON$/.test(key)) return 'boolean';