Restrict `linkip.adguard-dns.com` updates to only clients permitted by Access Settings

### Issue Details

When a device updates its IP address using the `linkip.adguard-dns.com` endpoint, the IP is linked to the device regardless of any configured server's Access Settings (Allowed / Disallowed Clients). Clients that should be blocked by Access Settings can still associate their IP with a device simply by calling the link‑IP endpoint.

### Proposed solution

IP linking via `linkip.adguard-dns.com` should respect Access Settings. If the requesting client is not allowed under the server’s Access Settings, its IP update request should be ignored or voided.

### Alternative solution

_No response_