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/admin/cashup/page.tsx

@@ -5,6 +5,7 @@ import { useRouter } from "next/navigation";
 import { useAuth } from "@/hooks/useAuth";
 import { apiFetch } from "@/lib/api";
 import { useDismissingState } from "@/hooks/useDismissingState";
+import { Wallet } from "lucide-react";
 
 export default function CashupLandingPage() {
   const { token } = useAuth();
@@ -46,14 +47,19 @@ export default function CashupLandingPage() {
 
   return (
     <div className="max-w-3xl mx-auto space-y-4">
-      <div className="flex items-center justify-between gap-3">
-        <div>
-          <h1 className="text-xl font-semibold">Post-event Cashup</h1>
-          <p className="text-sm text-gray-500 mt-1">Set costs, reconcile takings, and close out an event. Admin only.</p>
+      <div className="flex items-center justify-between gap-3 flex-wrap">
+        <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">
+            <Wallet className="w-5 h-5 text-brand-600" />
+          </div>
+          <div>
+            <h1 className="text-xl font-semibold text-gray-900">Post-event Cashup</h1>
+            <p className="text-sm text-gray-500 mt-1">Set costs, reconcile takings, and close out an event. Admin only.</p>
+          </div>
         </div>
         <button
           type="button"
-          className="px-3 py-1.5 text-sm rounded bg-gray-100 hover:bg-gray-200 text-gray-800 shrink-0"
+          className="px-3 py-1.5 text-sm rounded-lg bg-gray-100 hover:bg-gray-200 text-gray-800 shrink-0"
           onClick={() => router.push("/dashboard")}
         >Back</button>
       </div>
@@ -87,7 +93,7 @@ export default function CashupLandingPage() {
             return (
               <li
                 key={ev.id}
-                className="border rounded-lg p-3 bg-white hover:bg-indigo-50/40 cursor-pointer transition-colors flex items-center justify-between gap-3"
+                className="border rounded-lg p-3 bg-white hover:bg-brand-50/40 cursor-pointer transition-colors flex items-center justify-between gap-3"
                 onClick={() => router.push(`/dashboard/admin/cashup/${ev.id}`)}
               >
                 <div className="min-w-0">
@@ -101,7 +107,7 @@ export default function CashupLandingPage() {
                     {ev.startDate ? new Date(ev.startDate).toLocaleDateString() : ""}{ev.endDate ? ` – ${new Date(ev.endDate).toLocaleDateString()}` : ""}
                   </div>
                 </div>
-                <span className="text-xs text-indigo-600 shrink-0">Manage →</span>
+                <span className="text-xs text-brand-600 shrink-0">Manage →</span>
               </li>
             );
           })}