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/components/events/EventCard.tsx

@@ -1,5 +1,6 @@
 import { ApiImage } from "@/components/shared/ApiImage";
 import { Calendar } from "lucide-react";
+import { ContactButton } from "@/components/events/ContactButton";
 
  type Event = {
    id: string;
@@ -12,6 +13,10 @@ import { Calendar } from "lucide-react";
    price: number;
    picture?: string;
    isSoldOut?: boolean;
+   requiresRegistration?: boolean;
+   contactName?: string | null;
+   contactPhone?: string | null;
+   contactEmail?: string | null;
 };
 
 import { formatDateTimeRange } from "@/lib/date";
@@ -47,6 +52,15 @@ export const EventCard = ({ event }: { event: Event }) => {
                         View details
                     </a>
                     {(() => {
+                      if (event.requiresRegistration === false) {
+                        return (
+                          <ContactButton
+                            contactName={event.contactName}
+                            contactPhone={event.contactPhone}
+                            contactEmail={event.contactEmail}
+                          />
+                        );
+                      }
                       const now = new Date();
                       const end = new Date(event.endDate);
                       const deadline = event.registrationDeadline ? new Date(event.registrationDeadline) : null;