fix(02-review): WR-05 forward abort signal through vpnStatus()/dnsStatus()

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>

neode-ui/src/api/rpc-client.ts

@@ -1001,7 +1001,7 @@ class RPCClient {
   }
 
   // VPN
-  async vpnStatus(): Promise<{
+  async vpnStatus(signal?: AbortSignal): Promise<{
     connected: boolean
     provider?: string
     interface?: string
@@ -1021,6 +1021,7 @@ class RPCClient {
     return this.call({
       method: 'vpn.status',
       params: {},
+      signal,
       dedup: true, // read-only status; safe to collapse concurrent callers (PERF-02)
     })
   }
@@ -1082,7 +1083,7 @@ class RPCClient {
   }
 
   // DNS
-  async dnsStatus(): Promise<{
+  async dnsStatus(signal?: AbortSignal): Promise<{
     provider: string
     servers: string[]
     doh_enabled: boolean
@@ -1092,6 +1093,7 @@ class RPCClient {
     return this.call({
       method: 'network.dns-status',
       params: {},
+      signal,
       dedup: true, // read-only status; safe to collapse concurrent callers (PERF-02)
     })
   }