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/components/shared/StatCard.tsx

@@ -0,0 +1,71 @@
+"use client";
+
+import React from "react";
+import Link from "next/link";
+import { ArrowRight, ArrowUp, ArrowDown, type LucideIcon } from "lucide-react";
+import { TONES, type Tone } from "./tones";
+
+/** A "vs last month"-style delta line. `value` is a percentage; null means no baseline to compare against (shown as "New"). */
+export type StatDelta = { value: number | null; label?: string };
+
+/**
+ * Richer stat tile for dashboard KPI rows (icon chip + label + big value +
+ * optional delta + optional "View X" link) — scaffolding for Phase 2's
+ * dashboard rebuilds. Not the same component as reports/StatTile.tsx, which
+ * stays as-is for Reports' own denser tiles.
+ */
+export function StatCard({
+  icon: Icon,
+  label,
+  value,
+  tone = "brand",
+  href,
+  linkLabel,
+  delta,
+}: {
+  icon: LucideIcon;
+  label: string;
+  value: string | number;
+  tone?: Tone;
+  href?: string;
+  linkLabel?: string;
+  delta?: StatDelta;
+}) {
+  const t = TONES[tone] || TONES.brand;
+  return (
+    <div className="rounded-xl border border-gray-200 bg-white p-4 shadow-sm">
+      <div className="flex items-center gap-3">
+        <div className={"w-10 h-10 rounded-lg flex items-center justify-center shrink-0 " + t.bg}>
+          <Icon className={"w-5 h-5 " + t.icon} />
+        </div>
+        <div className="min-w-0">
+          <div className="text-xs text-gray-500 truncate">{label}</div>
+          <div className="text-xl font-semibold text-gray-900 truncate">{value}</div>
+        </div>
+      </div>
+      {delta && (
+        <div className={"mt-2 flex items-center gap-1 text-xs font-medium " + (delta.value == null ? "text-gray-400" : delta.value >= 0 ? "text-emerald-600" : "text-rose-600")}>
+          {delta.value == null ? (
+            <span>New this month</span>
+          ) : (
+            <>
+              {delta.value >= 0 ? <ArrowUp className="w-3 h-3" /> : <ArrowDown className="w-3 h-3" />}
+              <span>{Math.abs(delta.value).toFixed(0)}%</span>
+              <span className="text-gray-400 font-normal">{delta.label || "vs last month"}</span>
+            </>
+          )}
+        </div>
+      )}
+      {href && (
+        <Link href={href} className="mt-3 inline-flex items-center gap-1 text-xs font-medium text-brand-600 hover:underline">
+          {linkLabel || "View"}
+          <ArrowRight className="w-3 h-3" />
+        </Link>
+      )}
+    </div>
+  );
+}
+
+export function StatCardRow({ children }: { children: React.ReactNode }) {
+  return <div className="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-5 gap-4">{children}</div>;
+}