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/content/help/user-forms.tsx

@@ -0,0 +1,30 @@
+import React from "react";
+import { FileText, Save, CheckCircle2 } from "lucide-react";
+import { GuideItem } from "@/components/shared/GuideItem";
+import type { HelpContent } from "./types";
+
+/** Help content for /dashboard/user/forms. */
+export const userFormsHelpContent: HelpContent = {
+  title: "Attendee forms",
+  subtitle: "Fill in the details required for your tickets.",
+  tabs: [
+    {
+      key: "overview",
+      label: "Overview",
+      icon: FileText,
+      content: (
+        <div className="space-y-4">
+          <p>You&apos;ll see one form to fill in per main ticket on your registration. Already-submitted forms are shown read-only above the remaining ones.</p>
+          <div className="space-y-4">
+            <GuideItem icon={CheckCircle2} title="Submitting" tone="brand">
+              Submit is enabled once every required field across all remaining forms is filled in.
+            </GuideItem>
+            <GuideItem icon={Save} title="Save for later" tone="green">
+              Not ready to finish? Save your progress as a draft and come back to complete it before the event.
+            </GuideItem>
+          </div>
+        </div>
+      ),
+    },
+  ],
+};