refactor(dashboard): drop redundant PLATFORM_ORDER and misleading optional chain

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/views/Dashboard.vue

@@ -328,21 +328,15 @@ let refreshInterval = null
 const stats = computed(() => downloadsStore.stats)
 const recentActivity = computed(() => downloadsStore.recentActivity)
 
-// Fixed display order for platform health bars
-const PLATFORM_ORDER = [
-  'patreon', 'subscribestar', 'hentaifoundry',
-  'discord', 'pixiv', 'deviantart',
-]
-
 // Read threshold from settings, default 5 if unset
 const failureThreshold = computed(() =>
-  settingsStore.settings?.['dashboard.failure_threshold'] ?? 5
+  settingsStore.settings['dashboard.failure_threshold'] ?? 5
 )
 
 // Per-platform health for platforms with ≥1 enabled source
 const platformHealth = computed(() => {
   const enabled = sourcesStore.sources.filter(s => s.enabled)
-  return PLATFORM_ORDER
+  return supportedPlatforms
     .map(platform => {
       const sources = enabled.filter(s => s.platform === platform)
       if (sources.length === 0) return null