feat(admin): monitoring center

Sprint 26.

New features/admin/monitoring/ module + net-new /:lang/backoffice/monitoring
route + Dashboard Quick Action.

- Health section reuses AdminDashboardFacade.healthChecks directly (real
  data, unchanged since Sprint 19) instead of duplicating the logic
- unified AdminMonitoringEvent feed covering audit/security/login/
  failed-login/api/error/warning, category filter + search, 40 seeded
  synthetic entries (no logging backend exists anywhere in this system)
- mock queue depth/status cards, mock webhook delivery log
- intentionally kept separate from Sprint 24's per-transaction audit and
  Sprint 25's per-user audit - different scopes, no consolidation attempted

Also fixed a real type error: AdminDashboardQuickActionId's union was
missing 'users' and 'monitoring' (added when wiring those Quick Actions),
caught by ng build's template type-checking even though plain tsc --noEmit
passed - a reminder that ng build is the authoritative check here.

docs/ADMIN.md + docs/BACKEND.md (new item 15) updated.

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

docs/ADMIN.md

@@ -369,6 +369,28 @@ routes at all, this is a net-new admin section.
 - Wired into `AdminDashboardFacade`'s Quick Actions list (`dashboard.actionUsers`
   -> `/​:lang/backoffice/users`).
 
+## Sprint 26 - Monitoring (mock/local, health reuses real data)
+
+`features/admin/monitoring/`, single page at `/​:lang/backoffice/monitoring`
+(new Dashboard Quick Action).
+
+- **Health**: reuses `AdminDashboardFacade.healthChecks` directly (the same
+  real, non-mocked bootstrap-validation checks from Sprint 19's dashboard)
+  instead of duplicating the logic - this is the one section on this page
+  backed by real data.
+- **Audit / security / login / failed-login / API / error / warning
+  events**: one unified `AdminMonitoringEvent` feed (`category` + `level`
+  discriminators) with category filter + search, seeded with 40
+  deterministic synthetic entries by `AdminMonitoringLocalGateway` - no
+  logging backend exists anywhere in this system, so there is nothing real
+  to read from.
+- **Queue monitoring**: 3 mock named queues with depth + status.
+- **Webhook monitoring**: mock delivery log (endpoint/event/status/time).
+- This is deliberately a separate, system-wide log from the two
+  narrower-scoped audit trails added earlier: Sprint 24's per-transaction
+  audit and Sprint 25's per-user audit. No consolidation attempted - they
+  track different things.
+
 ## Known gaps / backend needs
 
 - **Dashboard metrics endpoint.** Categories/Products counts are computed

docs/BACKEND.md

@@ -160,6 +160,14 @@ Plus, if authenticated history/wishlist/compare/saved-searches sync is wanted: `
 
 **Frontend files:** implement `AdminUsersApiGateway` against `AdminUsersGateway` (`services/admin-users-gateway.interface.ts`) and rebind via an injection token.
 
+## 15. Monitoring (Sprint 26, mock/local except Health)
+
+**Current behavior:** `features/admin/monitoring/` — Health section reads real data (`AdminDashboardFacade.healthChecks`, unchanged from Sprint 19). Everything else (audit/security/login/failed-login/API/error/warning event feed, queue depths, webhook deliveries) is synthetic, seeded once in `AdminMonitoringLocalGateway` — no logging, queue, or webhook infrastructure exists anywhere in this system.
+
+**Needed:** real structured logging with a query API (by category/level/actor/time range), real queue introspection (whatever job runner ships), and real webhook delivery tracking once webhooks exist as a feature at all.
+
+**Frontend files:** implement `AdminMonitoringApiGateway`-equivalent methods against a to-be-defined `AdminMonitoringGateway` interface (`AdminMonitoringLocalGateway` currently has no interface extracted — add one when a real implementation is built, mirroring the pattern used everywhere else in `admin/*`).
+
 ## Known reliability issues
 
 ### Production 502/504 Bad Gateway on refresh / back-navigation

docs/SPRINT-PLAN.md

@@ -59,8 +59,9 @@ Notify user: **from Sprint 20 (Categories) once product↔category link + admin
 - [x] `docs/ADMIN.md` (new Sprint 25 section), `docs/BACKEND.md` item 14 added
 - Commit: `feat(admin): users and permissions`
 
-## Sprint 26 — Monitoring
-- [ ] Audit/security/login logs views (local), API/error/warning feed, queue/webhook placeholders, health page
+## Sprint 26 — Monitoring ✅ done
+- [x] Audit/security/login/failed-login logs (unified event feed, category filter), API/error/warning feed, queue/webhook mock views, health page (reuses real Sprint 19 healthChecks)
+- [x] `docs/ADMIN.md` (new Sprint 26 section), `docs/BACKEND.md` item 15 added
 - Commit: `feat(admin): monitoring center`
 
 ## Sprint 27 — Analytics