fix: TS type error in VPN status, remove unused assignment warning

- Fix vpnStatus type mismatch (provider: string|undefined vs string|null)
- Remove redundant history_dirty assignment in health_monitor.rs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/views/Home.vue

@@ -311,7 +311,7 @@ const torConnected = computed(() => {
   const torAddr = store.data?.['server-info']?.['tor-address']
   return !!torAddr && torAddr.length > 0
 })
-const vpnStatus = ref<{ connected: boolean; provider: string | null }>({ connected: false, provider: null })
+const vpnStatus = ref({ connected: false, provider: '' })
 const vpnConnected = computed(() => vpnStatus.value.connected || (!!packages.value['tailscale'] && packages.value['tailscale'].state === PackageState.Running))
 const bitcoinSyncDisplay = computed(() => {
   if (!systemStats.bitcoinAvailable) return 'Not running'
@@ -348,7 +348,7 @@ const cloudFolderDisplay = computed(() => cloudFolderCount.value !== null ? Stri
 onMounted(async () => {
   try { const usage = await fileBrowserClient.getUsage(); cloudStorageUsed.value = usage.totalSize; cloudFolderCount.value = usage.folderCount } catch { /* not running */ }
   loadSystemStats(); systemStatsInterval = setInterval(loadSystemStats, 30000); checkUpdateStatus(); loadWeb5Status()
-  rpcClient.vpnStatus().then(s => { vpnStatus.value = s }).catch(() => {})
+  rpcClient.vpnStatus().then(s => { vpnStatus.value = { connected: s.connected, provider: s.provider ?? '' } }).catch(() => {})
 })
 
 // Wallet modals