feat: add dashboard source code with Vite + React + Recharts and CI/CD build

- Reconstruct dashboard from compiled container: App.jsx, main.jsx, index.css
- nginx.conf with SPA routing and /api proxy to api:8000
- Multi-stage Dockerfile: node:20-alpine build + nginx:alpine serve
- Add third kaniko build step in ci.yml for chemavx/polymarket-bot-dashboard
- Update k8s manifest sed to patch deployment-dashboard.yaml image on each push

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

dashboard/vite.config.js

@@ -0,0 +1,14 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+
+export default defineConfig({
+  plugins: [react()],
+  server: {
+    proxy: {
+      '/api': {
+        target: 'http://api:8000',
+        changeOrigin: true,
+      },
+    },
+  },
+})