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/vite.config.ts

@@ -0,0 +1,28 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+import path from 'path'
+
+export default defineConfig({
+  plugins: [react()],
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+    },
+  },
+  build: {
+    outDir: '../meshai/dashboard/static',
+    emptyOutDir: true,
+  },
+  server: {
+    proxy: {
+      '/api': {
+        target: 'http://localhost:8080',
+        changeOrigin: true,
+      },
+      '/ws': {
+        target: 'ws://localhost:8080',
+        ws: true,
+      },
+    },
+  },
+})