server.network-summary's fetcher batches four RPCs but only two forwarded
the AbortSignal useCachedResource provides for abort-on-unmount;
rpcClient.vpnStatus()/dnsStatus() had no signal parameter at all, so
aborter.abort() couldn't cancel them, partially defeating the documented
abort-on-unmount contract for this resource.
Add an optional signal parameter to both convenience methods (mirroring
the pattern used throughout rpc-client.ts) and forward it from Server.vue.
Co-Authored-By: Claude <noreply@anthropic.com>
