Also log staff cancellations via PUT /api/registrations/:id

Registrations can be cancelled two ways: DELETE /:id (owner or admin,
already logged registration_cancelled) and PUT /:id (staff+, status
change endpoint) — the latter was silently unlogged. Since PUT /:id
is staff-only, any transition into 'cancelled' there is inherently a
staff-initiated cancellation, so it's now logged the same way.

Audited all six categories promised in the 1.10.0 changelog entry
(refunds, donation assign/unassign, manual registrations,
staff-initiated cancellations, event create/update/delete, settings
changes) against their actual logAdminAction call sites and route
wiring — this was the only other gap found.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSWFWQsjTc9GyffPiXEDQT

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project follows [Semantic Versioning](https://semver.org/).
 ### Fixed
 
 - Creating an event was never recorded in the admin audit log — 1.10.0 added `event_created` as a logged action on the frontend's filter list, but the backend's `createEvent` never actually called `logAdminAction`, only `updateEvent`/`deleteEvent` did. Event creation is now logged the same way.
+- Staff cancelling a registration via `PUT /api/registrations/:id` (the staff status-change endpoint, separate from the owner-facing `DELETE /:id` cancel route) wasn't logged at all — only the `DELETE` path logged `registration_cancelled`. Both paths now log it, verified against all six audit categories promised in 1.10.0 (refunds, donation assign/unassign, manual registrations, staff-initiated cancellations, event create/update/delete, settings changes) with no other gaps found.
 - Added a "Back to dashboard" link to Admin → Audit log, matching the back-link pattern already used on the Cashup page.
 
 ## [1.10.2] - 2026-08-28