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/Dockerfile

@@ -0,0 +1,19 @@
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY package.json .
+RUN npm install
+
+COPY index.html .
+COPY vite.config.js .
+COPY src/ ./src/
+
+RUN npm run build
+
+FROM nginx:alpine
+
+COPY --from=builder /app/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80