Simplify registration flow: mandatory signup redirect, payment emails, payment reminder cron

- EventRegistrationForm/WatcherForm/PerformerForm: remove session/login nudge/SuccessScreen;
  both roles redirect to /login?signup=1&email=<email>&next=/account after submit
- SuccessScreen.tsx deleted (no longer used)
- account.tsx: add 'Betaal nu' CTA via checkoutMutation (shown when watcher + paymentStatus pending)
- DB schema: add paymentReminderSentAt column to registration table
- Migration: 0008_payment_reminder_sent_at.sql
- email.ts: update registrationConfirmationHtml / sendConfirmationEmail with signupUrl param;
  add sendPaymentReminderEmail and sendPaymentConfirmationEmail functions
- routers/index.ts: wire payment reminder into runSendReminders() — queries watchers
  with paymentStatus pending, paymentReminderSentAt IS NULL, createdAt <= now-3days
- mollie.ts webhook: call sendPaymentConfirmationEmail after marking registration paid

packages/api/src/routers/index.ts

@@ -10,6 +10,7 @@ import { z } from "zod";
 import {
 	sendCancellationEmail,
 	sendConfirmationEmail,
+	sendPaymentReminderEmail,
 	sendReminderEmail,
 	sendUpdateEmail,
 } from "../email";
@@ -975,5 +976,40 @@ export async function runSendReminders(): Promise<{
 		}
 	}
 
+	// Payment reminders: watchers with pending payment older than 3 days
+	const threeDaysAgo = now - 3 * 24 * 60 * 60 * 1000;
+	const unpaidWatchers = await db
+		.select()
+		.from(registration)
+		.where(
+			and(
+				eq(registration.registrationType, "watcher"),
+				eq(registration.paymentStatus, "pending"),
+				isNull(registration.paymentReminderSentAt),
+				lte(registration.createdAt, new Date(threeDaysAgo)),
+			),
+		);
+
+	for (const reg of unpaidWatchers) {
+		if (!reg.managementToken) continue;
+		try {
+			await sendPaymentReminderEmail({
+				to: reg.email,
+				firstName: reg.firstName,
+				managementToken: reg.managementToken,
+				drinkCardValue: reg.drinkCardValue ?? undefined,
+				giftAmount: reg.giftAmount ?? undefined,
+			});
+			await db
+				.update(registration)
+				.set({ paymentReminderSentAt: new Date() })
+				.where(eq(registration.id, reg.id));
+			sent++;
+		} catch (err) {
+			errors.push(`payment-reminder ${reg.email}: ${String(err)}`);
+			console.error(`Failed to send payment reminder to ${reg.email}:`, err);
+		}
+	}
+
 	return { sent, skipped: false, errors };
 }