fix(zt-gateway): prevent health dots flashing red on each poll cycle

Cache last-known health state per region so renderGatewayRow uses
correct values instead of defaulting to unreachable. Parallelize
refreshHealth with Promise.all so all gateway pings resolve together
instead of sequentially (3 gateways × -W 3 timeout was ~18s worst case).

htdocs/luci-static/resources/view/zt-gateway/overview.js

@@ -59,7 +59,8 @@ function ubusSetup(command) {
 return view.extend({
 	state: {
 		selectedRegion: null,
-		switchMode: 'force'
+		switchMode: 'force',
+		healthCache: {}
 	},
 
 	load() {
@@ -87,11 +88,14 @@ return view.extend({
 				change: ev => this.onSelectRegion(ev.target.value),
 				checked: isSelected || null,
 			})),
-			E('td', { class: 'zt-region-cell' }, [
-				this.renderHealthDot(false, null),
-				' ',
+			(() => {
+				const cached = this.state.healthCache[gw.region];
+				const dot = this.renderHealthDot(cached ? cached.reachable : false, cached ? cached.latency_ms : null);
+				return E('td', { class: 'zt-region-cell' }, [
+					dot, ' ',
 					isActive ? E('strong', {}, gw.region) : document.createTextNode(gw.region)
-			]),
+				]);
+			})(),
 			E('td', {}, gw.label),
 			E('td', {}, gw.ip),
 			E('td', {}, isActive ? E('em', {}, _('active')) : '')
@@ -250,25 +254,34 @@ return view.extend({
 
 	async refreshHealth(data) {
 		const gws = data.gateways || [];
-		for (let i = 0; i < gws.length; i++) {
-			const region = gws[i].region;
-			try {
-				const h = await ubusHealth(region);
+		const checks = gws.map(gw => {
+			return ubusHealth(gw.region).then(h => {
+				if (h) {
+					this.state.healthCache[gw.region] = {
+						reachable: !!h.reachable,
+						latency_ms: h.latency_ms ?? null
+					};
+				}
+				return { region: gw.region, h };
+			}).catch(() => {
+				this.state.healthCache[gw.region] = { reachable: false, latency_ms: null };
+				return { region: gw.region, h: null };
+			});
+		});
+
+		const results = await Promise.all(checks);
+		for (const { region, h } of results) {
+			if (!h) continue;
 			const row = document.querySelector('.zt-gateway-row[data-region="%s"]'.format(region));
-				if (row && h) {
+			if (!row) continue;
 			const node = row.querySelector('.zt-health');
-					if (node) {
+			if (!node) continue;
 			node.classList.toggle('zt-health-up', !!h.reachable);
 			node.classList.toggle('zt-health-down', !h.reachable);
 			node.title = h.reachable && h.latency_ms != null
 				? _('UP (%sms)').format(h.latency_ms)
 				: (h.reachable ? _('UP') : _('DOWN'));
 		}
-			}
-			} catch (_) {
-				/* health check is best-effort */
-			}
-		}
 	},
 
 	async refreshState() {