Fix early-bird price blending and mislabeling; add contact-only events

- Early-bird pricing: RegistrationOption now tracks each purchase as a
  separate price tranche instead of overwriting a single price/quantity
  on repeat purchases, so buying more tickets after a tier expires no
  longer re-prices tickets already bought at the old price. Stock-limit
  checks, total-due calculation, and the Finance report's revenue-by-
  option are all tranche-aware; pages that showed one blended price per
  line now render/total each tranche. Viewing a pending/partially-paid
  registration (dashboard, detail page, or an event's registration
  list) now refreshes stale pricing on the spot instead of only at
  payment time.
- Fixed the "(early bird)" dashboard label incorrectly firing on any
  line priced below the base option price (e.g. a plain cheaper
  variant) — it now checks the real applied-tier flag.
- Added contact-only events (e.g. baptism): no registration/payment
  flow, shown on the public site with a "Contact us" popup instead of
  a Register button. Configurable via the admin event wizard.

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

frontend/src/app/events/[id]/page.tsx

@@ -2,6 +2,7 @@ import { notFound } from "next/navigation";
 import { Navbar } from "@/components/layout/Navbar";
 import { Footer } from "@/components/layout/Footer";
 import ClientActions from "@/app/events/[id]/ClientActions";
+import { ContactButton } from "@/components/events/ContactButton";
 import { Calendar, Ticket, Paperclip, Sparkles } from "lucide-react";
 
 export const revalidate = 60;
@@ -32,6 +33,10 @@ type Event = {
   eventOptions?: EventOption[];
   attachments?: EventAttachment[];
   requiresAuth?: boolean;
+  requiresRegistration?: boolean;
+  contactName?: string | null;
+  contactPhone?: string | null;
+  contactEmail?: string | null;
 };
 
 import { apiFetch, ApiError } from "@/lib/api";
@@ -51,6 +56,16 @@ function lowStockThreshold(stockLimit: number): number {
 }
 
 function RegisterCta({ event }: { event: Event }) {
+  if (event.requiresRegistration === false) {
+    return (
+      <ContactButton
+        contactName={event.contactName}
+        contactPhone={event.contactPhone}
+        contactEmail={event.contactEmail}
+        className="block w-full text-center bg-brand-600 text-white px-4 py-2.5 rounded-lg hover:bg-brand-700 font-medium transition-colors"
+      />
+    );
+  }
   const now = new Date();
   const end = new Date(event.endDate);
   const deadline = event.registrationDeadline ? new Date(event.registrationDeadline) : null;