Full site redesign, help system, and dashboard stats fixes

Multi-phase visual facelift (design tokens, dashboards, sidebar/navbar
shell, per-page help guides, and a layout/content pass across every
remaining page) plus backend fixes to the dashboard KPI stats:

- Admin/Supervisor dashboard KPIs (revenue, donations, registrations,
  tickets sold) now use a rolling trailing-month window (today back one
  calendar month, e.g. 9 May - 8 June if today is 8 June) instead of
  calendar month-to-date, which under-counted for most of the month.
  The comparison window shifts the same way, so like is still compared
  with like.
- Reports deep-links from those stat tiles now match the same window
  (range=trailing_month, replacing range=this_month).
- Design tokens (brand-* Tailwind scale + shadcn CSS variables), a
  site-wide contextual help button, fixed dashboard sidebar/navbar,
  Admin/Supervisor/Staff/User dashboard rebuilds backed by a new
  GET /api/stats/overview endpoint, a dedicated Contact page, Site
  Settings restyle with WhatsApp config folded in, and an Account
  activity feed backed by a new SecurityEvent model.
- Every remaining page (home, events, registration flow, auth, legal,
  payment results, and every Admin/Supervisor/Staff/User tool page)
  restyled onto the same design tokens, several with real layout
  upgrades (home hero, events list/detail, donate page, auth pages).
- 20+ new dedicated help guides so the whole site has page-specific
  help content instead of falling back to a generic guide.
- Assorted fixes surfaced along the way: donation-leg double-counting
  in payment stats, donations not counting toward revenue, refund
  netting in per-method report breakdowns, and donation
  over-allocation after a refund.

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

frontend/src/app/dashboard/user/payments/page.tsx

@@ -6,6 +6,7 @@ import { apiFetch } from "@/lib/api";
 import { useDismissingState } from "@/hooks/useDismissingState";
 import { formatDateTime } from "@/lib/date";
 import { formatPaymentMethod } from "@/lib/paymentMethod";
+import { Receipt } from "lucide-react";
 
 interface PaymentItem {
   id: string;
@@ -74,10 +75,15 @@ export default function UserPaymentsPage() {
 
   return (
     <div className="max-w-4xl mx-auto w-full px-4 py-6 sm:px-6">
-      <div className="flex items-center justify-between mb-4">
-        <h1 className="text-2xl font-semibold">My Payments</h1>
+      <div className="flex items-center justify-between mb-4 flex-wrap gap-3">
+        <div className="flex items-center gap-3">
+          <div className="w-10 h-10 rounded-xl bg-brand-50 flex items-center justify-center shrink-0">
+            <Receipt className="w-5 h-5 text-brand-600" />
+          </div>
+          <h1 className="text-2xl font-semibold text-gray-900">My Payments</h1>
+        </div>
         <button
-          className="px-2.5 py-1 text-xs rounded bg-gray-100 hover:bg-gray-200 text-gray-800 shadow-sm focus:outline-none focus:ring-2 focus:ring-blue-500 focus:ring-offset-1"
+          className="px-2.5 py-1 text-xs rounded-lg bg-gray-100 hover:bg-gray-200 text-gray-800 shadow-sm focus:outline-none focus:ring-2 focus:ring-brand-500 focus:ring-offset-1"
           onClick={() => router.push("/dashboard/user")}
         >Back to dashboard</button>
       </div>
@@ -183,7 +189,7 @@ export default function UserPaymentsPage() {
                   ) : (
                     <button
                       key={p}
-                      className={`px-2 py-1 rounded ${page === p ? "bg-indigo-600 text-white" : "bg-gray-100 hover:bg-gray-200"}`}
+                      className={`px-2 py-1 rounded ${page === p ? "bg-brand-600 text-white" : "bg-gray-100 hover:bg-gray-200"}`}
                       disabled={fetching}
                       onClick={() => goToPage(p as number)}
                     >{p}</button>