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

src/models/calendar/events/events.service.ts

@@ -126,6 +126,64 @@ export const getAllEventsAdmin = async (calendarId: number): Promise<Event[]> =>
 	}
 };
 
+/**
+ * Returns a single event by id (latest version, any status), or null if it
+ * doesn't exist. Unlike getAllEvents/getAllEventsAdmin this isn't scoped to
+ * a calendar - callers that need to enforce calendar/status visibility
+ * should check the returned event's calendarId/status themselves.
+ * @param eventId The event id
+ */
+export const getEventById = async (eventId: number): Promise<Event | null> => {
+	let conn = await NachklangCalendarDB.getConnection();
+	try {
+		const eventsQuery = `
+		SELECT e.calendar_id, e.uuid, e.created_date, e.created_by_id, u.full_name as created_by_name, u2.full_name as last_modified_by_name, v.* FROM events e
+			INNER JOIN (
+  				SELECT event_id, MAX(event_version_id) AS latest_version
+			  	FROM event_versions
+			  	GROUP BY event_id
+			) latest_versions
+			ON e.event_id = latest_versions.event_id
+			INNER JOIN event_versions v
+			ON v.event_id = latest_versions.event_id AND v.event_version_id = latest_versions.latest_version
+			LEFT OUTER JOIN users u ON u.user_id = e.created_by_id
+		    LEFT OUTER JOIN users u2 ON u2.user_id = v.version_created_by_id
+			WHERE e.event_id = ?`;
+		const eventsRes = await conn.query(eventsQuery, eventId);
+
+		if (eventsRes.length === 0) {
+			return null;
+		}
+
+		const row = eventsRes[0];
+		return {
+			eventId: row.event_id,
+			calendarId: row.calendar_id,
+			uuid: row.uuid,
+			name: row.name,
+			description: row.description,
+			startDateTime: row.start_datetime,
+			endDateTime: row.end_datetime,
+			createdDate: row.created_date,
+			lastModifiedDate: row.version_created_at,
+			location: row.location,
+			createdBy: row.created_by_name,
+			createdById: row.created_by_id,
+			lastModifiedBy: row.last_modified_by_name,
+			lastModifiedById: row.version_created_by_id,
+			url: row.url,
+			wholeDay: row.whole_day,
+            repeatFrequency: row.repeat_frequency,
+			status: row.status
+		} as Event;
+	} catch (err) {
+		throw err;
+	} finally {
+		// Return connection
+		await conn.end();
+	}
+};
+
 /**
  * Create the given event in the database
  * @param event The event to create