feat(dashboard): React frontend scaffold with overview page

- Vite + React 18 + TypeScript + Tailwind CSS
- Dashboard overview with health gauge, pillar bars, alerts
- WebSocket hook for real-time updates
- Layout with sidebar navigation and live indicator
- Placeholder pages for Mesh, Environment, Config, Alerts
- Dark theme ops center aesthetic with JetBrains Mono

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dashboard-frontend/src/index.css

@@ -0,0 +1,49 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+body {
+  background: #0a0e17;
+  margin: 0;
+  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+/* Custom scrollbar */
+::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+::-webkit-scrollbar-track {
+  background: #0a0e17;
+}
+
+::-webkit-scrollbar-thumb {
+  background: #2d3a4d;
+  border-radius: 4px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: #3b4a5d;
+}
+
+/* Data values use JetBrains Mono */
+.font-mono {
+  font-family: 'JetBrains Mono', monospace;
+}
+
+/* Pulsing animation for live indicator */
+@keyframes pulse {
+  0%, 100% {
+    opacity: 1;
+  }
+  50% {
+    opacity: 0.5;
+  }
+}
+
+.animate-pulse-slow {
+  animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite;
+}