Add Tickets domain for the voucher-based ticket shop

New domain mirroring the Feedback module's conventions: single-use voucher
codes (wildcard + personalized), redemption with race-safe capacity and
deadline enforcement, admin CRUD for vouchers/redemptions/event settings
with an audit trail, and reuse of the existing Calendar session auth.

Backend pieces:
- Tickets domain (public redeem flow, admin vouchers/redemptions/events)
- Calendar events.service.ts: add getEventById
- Mailer: attachment/HTML support, fix a shared-mutable-state race
- Per-event capacity/deadline/address settings, with an "address
  required" option on top of "address collected"
- Email format validation on redeem and admin voucher/redemption input
- Docker Compose dev stack (MariaDB + seed data) for local testing

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

src/models/tickets/Tickets.router.ts

@@ -0,0 +1,8 @@
+import express from 'express';
+import {adminRouter} from './admin/admin.router';
+import {publicRouter} from './public/public.router';
+
+export const ticketsRouter = express.Router();
+
+ticketsRouter.use('/admin', adminRouter);
+ticketsRouter.use('/', publicRouter);