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/STATE.md

@@ -0,0 +1,50 @@
+# Project State
+
+## Project Reference
+
+See: .paul/PROJECT.md (updated 2026-04-19)
+
+**Core value:** Uzytkownicy moga szybko i bezpiecznie kupic bilety online oraz otrzymac natychmiastowe potwierdzenie zakupu.
+**Current focus:** v0.1 Initial Release complete - ready for next milestone planning
+
+## Current Position
+
+Milestone: v0.1 Initial Release
+Phase: 1 of 1 (Purchase Data Layer) - Complete
+Plan: 01-01 complete
+Status: Loop closed, ready for next PLAN
+Last activity: 2026-04-19 20:31 - Completed UNIFY and phase transition for 01-01
+
+Progress:
+- Milestone: [##########] 100%
+- Phase 1: [##########] 100%
+
+## Loop Position
+
+Current loop state:
+```
+PLAN --> APPLY --> UNIFY
+  x        x        x     [Loop complete - ready for next PLAN]
+```
+
+## Accumulated Context
+
+### Decisions
+- 2026-04-19: Event `purchase` emitowany na `order-confirm`, nie na `przelewy24` (eliminuje falszywe konwersje).
+- 2026-04-19: Payload ecommerce budowany w backendzie i serializowany bezpiecznie do widoku.
+
+### Deferred Issues
+None yet.
+
+### Blockers/Concerns
+None yet.
+
+## Session Continuity
+
+Last session: 2026-04-19 20:32
+Stopped at: Phase 1 complete and unified
+Next action: Start next milestone planning ($paul-milestone or $paul-plan after roadmap update)
+Resume file: .paul/ROADMAP.md
+
+---
+*STATE.md - Updated after every significant action*