feat: add recurring transactions (Wiederkehrende Buchungen)

Lets treasurers/captains/coaches define recurring fee/levy dues that
are automatically booked for all active players on a monthly,
quarterly, or yearly schedule via a daily cron job, instead of having
to book them manually every cycle.

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

myteamwallet_backend/src/recurring-transactions/recurring-transaction-interval.enum.ts

@@ -0,0 +1,5 @@
+export enum RecurringTransactionIntervalEnum {
+  'monthly' = 'monthly',
+  'quarterly' = 'quarterly',
+  'yearly' = 'yearly',
+}