feat: registry health indicator

Show colored dot next to each registry name:
- Yellow (pulsing): checking connectivity
- Green: connected and reachable
- Red: unreachable or auth failed

Health is checked automatically when the registries page loads
and updated when "Test Connection" is clicked.

web/src/routes/settings/registries/+page.svelte

@@ -20,6 +20,7 @@
 	let formOwner = $state('');
 	let formSaving = $state(false);
 	let testingId = $state<string | null>(null);
+	let healthStatus = $state<Record<string, 'checking' | 'healthy' | 'unhealthy'>>({});
 
 	let errors = $state<Record<string, string>>({});
 
@@ -37,7 +38,11 @@
 
 	async function loadRegistryList() {
 		loading = true;
-		try { registries = await listRegistries(); } catch (err) { toasts.error(err instanceof Error ? err.message : $t('settingsRegistries.loadFailed')); } finally { loading = false; }
+		try {
+			registries = await listRegistries();
+			// Check health of all registries in the background.
+			checkAllHealth();
+		} catch (err) { toasts.error(err instanceof Error ? err.message : $t('settingsRegistries.loadFailed')); } finally { loading = false; }
 	}
 
 	async function handleSave() {
@@ -61,9 +66,26 @@
 
 	async function handleTestConnection(registry: Registry) {
 		testingId = registry.id;
-		try { await testRegistry(registry.id); toasts.success($t('settingsRegistries.testSuccess', { name: registry.name })); }
-		catch (err) { toasts.error(err instanceof Error ? err.message : $t('settingsRegistries.testFailed')); }
-		finally { testingId = null; }
+		try {
+			await testRegistry(registry.id);
+			toasts.success($t('settingsRegistries.testSuccess', { name: registry.name }));
+			healthStatus[registry.id] = 'healthy';
+		} catch (err) {
+			toasts.error(err instanceof Error ? err.message : $t('settingsRegistries.testFailed'));
+			healthStatus[registry.id] = 'unhealthy';
+		} finally { testingId = null; }
+	}
+
+	async function checkAllHealth() {
+		for (const reg of registries) {
+			healthStatus[reg.id] = 'checking';
+			try {
+				await testRegistry(reg.id);
+				healthStatus[reg.id] = 'healthy';
+			} catch {
+				healthStatus[reg.id] = 'unhealthy';
+			}
+		}
 	}
 
 	$effect(() => { loadRegistryList(); });
@@ -134,6 +156,13 @@
 				<div class="flex items-center justify-between rounded-xl border border-[var(--border-primary)] bg-[var(--surface-card)] p-4 shadow-[var(--shadow-sm)] transition-all duration-150 hover:shadow-[var(--shadow-md)]">
 					<div>
 						<div class="flex items-center gap-2">
+							{#if healthStatus[registry.id] === 'checking'}
+								<span class="h-2.5 w-2.5 shrink-0 rounded-full bg-yellow-400 animate-pulse" title="Checking..."></span>
+							{:else if healthStatus[registry.id] === 'healthy'}
+								<span class="h-2.5 w-2.5 shrink-0 rounded-full bg-emerald-500" title="Connected"></span>
+							{:else if healthStatus[registry.id] === 'unhealthy'}
+								<span class="h-2.5 w-2.5 shrink-0 rounded-full bg-red-500" title="Unreachable"></span>
+							{/if}
 							<h3 class="text-sm font-semibold text-[var(--text-primary)]">{registry.name}</h3>
 							<span class="rounded-full bg-[var(--surface-card-hover)] px-2 py-0.5 text-xs font-medium text-[var(--text-tertiary)]">{registry.type}</span>
 						</div>