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>

backend/src/utils/cashupUtils.js

@@ -83,7 +83,7 @@ async function computeEventFinancials(eventId) {
     }),
     prisma.registrationOption.findMany({
       where: { registration: { eventId, status: 'paid' } },
-      include: { eventOption: { select: { id: true, name: true, price: true } } }
+      include: { eventOption: { select: { id: true, name: true, price: true } }, tranches: true }
     }),
     prisma.eventCashup.findMany({
       where: { eventId },
@@ -191,15 +191,17 @@ async function computeEventFinancials(eventId) {
   const effectiveTotalRevenue = ALL_METHODS.reduce((s, m) => s + effectiveGrossIncomeByMethod[m], 0);
   const netProfit = effectiveTotalRevenue - totalCosts;
 
-  // What was actually sold, by ticket type — for the Finance report's income-stream breakdown
+  // What was actually sold, by ticket type — for the Finance report's income-stream breakdown.
+  // Revenue is tranche-aware: a line spanning two early-bird prices contributes each tranche
+  // at the price it was actually bought at, not one blended/stale price for the whole line.
+  const { computeOptionLineTotal } = require('./pricing');
   const salesByOptionMap = {};
   for (const ro of salesRows) {
     const opt = ro.eventOption;
     if (!opt) continue;
     if (!salesByOptionMap[opt.id]) salesByOptionMap[opt.id] = { eventOptionId: opt.id, name: opt.name, quantitySold: 0, revenue: 0 };
-    const unitPrice = ro.priceSnapshot != null ? ro.priceSnapshot : opt.price;
     salesByOptionMap[opt.id].quantitySold += ro.quantity;
-    salesByOptionMap[opt.id].revenue += unitPrice * ro.quantity;
+    salesByOptionMap[opt.id].revenue += computeOptionLineTotal(ro, null, new Date());
   }
   const salesByOption = Object.values(salesByOptionMap);