Help guide opens on demand only; add At the door to admin quick actions

- The site-wide help guide no longer auto-opens on first visit to a page
  — it only opens when the help button is clicked. Removed the
  now-pointless "Don't show this again" checkbox and the per-page
  dismissal tracking it drove.
- Admin dashboard quick actions was missing "At the door" (walk-in
  registration, payments, ticket printing), which Supervisor already had.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/app/dashboard/admin/page.tsx

@@ -8,7 +8,7 @@ import { useStableState } from "@/hooks/useStableState";
 import { useVisiblePolling } from "@/hooks/useVisiblePolling";
 import {
   Calendar, Banknote, Gift, Users, Ticket, QrCode, ClipboardList,
-  UserPlus, FileText, MessageCircle, BarChart2, Mail, Wallet,
+  UserPlus, FileText, MessageCircle, BarChart2, Mail, Wallet, DoorOpen,
 } from "lucide-react";
 import { StatCard, StatCardRow } from "@/components/shared/StatCard";
 import { QuickActionTile, QuickActionGrid } from "@/components/shared/QuickActionTile";
@@ -25,6 +25,7 @@ const QUICK_ACTIONS = [
   { href: "/dashboard/supervisor/events", label: "Manage events", description: "Create, edit, and update ticket types", icon: Calendar },
   { href: "/dashboard/admin/registrations", label: "Manage registrations", description: "Cancel, update status, and search registrations", icon: ClipboardList },
   { href: "/dashboard/supervisor/manual", label: "Manual registration", description: "Register a guest and issue tickets", icon: UserPlus },
+  { href: "/dashboard/supervisor/at-the-door", label: "At the door", description: "Walk-ins, payments, ticket printing", icon: DoorOpen },
   { href: "/dashboard/supervisor/payments", label: "Payments & donations", description: "Manual payments and assignment", icon: Wallet },
   { href: "/dashboard/staff/ticket-scanning", label: "Open scanner", description: "Use your device camera to validate tickets", icon: QrCode },
   { href: "/dashboard/supervisor/reports", label: "Reports", description: "View, export, and email reports", icon: BarChart2 },