feat(admin): transaction management

Sprint 24.

New features/admin/transactions/ module. AdminTransactionsLocalGateway
derives one synthetic transaction per Sprint 23's seeded mock order rather
than a separate dataset, keeping order numbers/totals consistent across
the two mock feature areas.

- list: search, status filter, type filter (payment/refund/qr_payment),
  pagination, CSV export
- retry failed transactions (appends an audit entry)
- fraud flag toggle
- per-transaction audit log (creation/retry/fraud-flag-change), viewed via
  dialog - intentionally separate from the system-wide audit/security log
  planned for Sprint 26 (Monitoring)
- wired into /:lang/backoffice/transactions, replacing the coming-soon
  placeholder

docs/ADMIN.md + docs/BACKEND.md (new item 13) updated.

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

docs/ADMIN.md

@@ -314,6 +314,27 @@ container/facade/service split as the rest of `admin/*`:
 - Wired into `/​:lang/backoffice/orders` and `/​:lang/backoffice/orders/:id`,
   replacing the coming-soon placeholder.
 
+## Sprint 24 - Transactions (mock/local)
+
+`features/admin/transactions/`. `AdminTransactionsLocalGateway` derives its
+mock data from `AdminOrdersLocalGateway`'s 24 seeded orders (one
+transaction per order, deterministic type/status/method assignment) rather
+than a separate synthetic dataset - keeps order numbers/totals consistent
+between the two mock feature areas.
+
+- List: search, status filter, type filter (payment/refund/qr_payment),
+  pagination, CSV export.
+- Retry failed transactions (`status: 'failed' -> 'retried'`, appends an
+  audit entry).
+- Fraud flag toggle per transaction.
+- Audit log: each transaction carries its own `audit: AdminTransactionAuditEntry[]`
+  (creation, retries, fraud-flag changes), viewed via a dialog - this is a
+  per-transaction audit trail, not the system-wide audit/security log
+  planned for Sprint 26 (Monitoring); the two are intentionally separate
+  scopes.
+- Wired into `/​:lang/backoffice/transactions`, replacing the coming-soon
+  placeholder.
+
 ## Known gaps / backend needs
 
 - **Dashboard metrics endpoint.** Categories/Products counts are computed

docs/BACKEND.md

@@ -144,6 +144,14 @@ Plus, if authenticated history/wishlist/compare/saved-searches sync is wanted: `
 
 ---
 
+## 13. Transactions (Sprint 24, mock/local)
+
+**Current behavior:** `features/admin/transactions/` exists (list, retry-failed, fraud flag, per-transaction audit log, CSV export) against `AdminTransactionsLocalGateway`, which derives one synthetic transaction per seeded mock order from item 7's `AdminOrdersLocalGateway` — no real payment/transaction data exists.
+
+**Needed:** a real payments/transactions domain (card, QR, cash-on-delivery), linked to orders, with retry semantics matching whatever the actual payment provider supports, and fraud-flag persistence.
+
+**Frontend files:** implement `AdminTransactionsApiGateway` against `AdminTransactionsGateway` (`services/admin-transactions-gateway.interface.ts`) and rebind via an injection token.
+
 ## Known reliability issues
 
 ### Production 502/504 Bad Gateway on refresh / back-navigation

docs/SPRINT-PLAN.md

@@ -47,8 +47,9 @@ Notify user: **from Sprint 20 (Categories) once product↔category link + admin
 - [x] `docs/ADMIN.md` (new Sprint 23 section), `docs/BACKEND.md` item 7 rewritten
 - Commit: `feat(admin): order management`
 
-## Sprint 24 — Transactions (mock/local)
-- [ ] Payments/refunds/QR list, status, history, export, filters, search, retry, fraud flags, audit log view
+## Sprint 24 — Transactions (mock/local) ✅ done
+- [x] Payments/refunds/QR list, status, history (derived from Sprint 23's seeded orders), export, filters, search, retry failed, fraud flags, per-transaction audit log dialog
+- [x] `docs/ADMIN.md` (new Sprint 24 section), `docs/BACKEND.md` item 13 added
 - Commit: `feat(admin): transaction management`
 
 ## Sprint 25 — Users & Roles