v2.2.1: frontend closed-source + Docker one-click deploy

- Remove frontend source code (now in private repo)
- Add pre-built frontend/dist/ with Nginx serving
- Simplify docker-compose.yml (no Node.js build needed)
- Update README with docs index and Docker deploy guide
- Add admin order list and AI analysis stats tabs
- Add quick trade API routes
- Clean up redundant files (package-lock.json, yarn.lock, .iml)
- Add GitHub Actions workflow for frontend update automation

frontend/Dockerfile

@@ -0,0 +1,13 @@
+# QuantDinger Frontend - Pre-built Static Files
+# No build step needed - dist/ is already compiled.
+FROM nginx:1.25-alpine
+
+# Copy pre-built frontend files
+COPY dist/ /usr/share/nginx/html/
+
+# Copy nginx configuration
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]