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/package.json

@@ -0,0 +1,20 @@
+{
+  "name": "polymarket-dashboard",
+  "private": true,
+  "version": "1.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "react": "^18.2.0",
+    "react-dom": "^18.2.0",
+    "recharts": "^2.12.4"
+  },
+  "devDependencies": {
+    "@vitejs/plugin-react": "^4.2.1",
+    "vite": "^5.2.0"
+  }
+}