feat(01-purchase-data-layer): add post-payment purchase data layer

Phase 1 complete:

- move purchase event to order confirmation after successful payment

- add backend purchase payload builder for transaction and ticket lines

- remove premature purchase push from przelewy24 redirect view

.paul/docs/TODO.md

@@ -0,0 +1,4 @@
+# TODO
+
+> Luzny parking pomyslow, rzeczy do sprawdzenia, rzeczy ktore moga nigdy nie byc wdrozone.
+> Nie wymaga formalnosci - wrzucaj co chcesz.