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/calendar/events/event.interface.ts

@@ -70,9 +70,9 @@
  *           description: The ID of the user who created the event
  *           example: 456
  *         lastModifiedBy:
- *         	 type: string
- *         	 description: The name of the user who last modified the event
- *         	 example: "John Doe"
+ *           type: string
+ *           description: The name of the user who last modified the event
+ *           example: "John Doe"
  *         lastModifiedById:
  *           type: integer
  *           description: The ID of the user who last modified the event