Audit log pages should support "load more" pagination

Audit log pages load a fixed batch of 200 entries and stop there. If there's more history, you just don't see it. The UI already has a "Load more..." button stubbed out in the `AuditLog.vue` component, but it's not actually wired up.

## Current state

* All audit log pages (instance, device, team, platform) use an accordion-based timeline UI grouped by date, not a data table. Traditional page-based pagination doesn't fit this pattern.
* Each page fetches 200 entries in a single request and that's it.
* The backend already supports cursor-based pagination on all audit log endpoints and returns `next_cursor` in the response when there's more data.
* The shared `AuditLog.vue` component has a "Load more..." button (line 18) that shows when `nextCursor` is truthy, but `nextCursor` is hardcoded to `false` (line 95, there's a TODO). The `loadMore()` method emits a `load-more` event but no parent component listens for it.

## What needs to happen

* Wire up the existing "load more" button in `AuditLog.vue` so it actually works. The `next_cursor` from the API response needs to flow into the component and trigger subsequent fetches that append to the existing entries.
* Each parent page (instance `AuditLog.vue`, device `AuditLog.vue`, team `AuditLog.vue`, admin `AuditLog.vue`) needs to handle the `load-more` event by calling the API with the cursor and appending the results.
* Most of the pieces are already in place on both frontend and backend, this is largely a matter of connecting them.