Add React frontend for energy trading system

Implements React + TypeScript UI with Vite and Tailwind CSS.
Features dashboard with real-time WebSocket updates, backtesting
page, model management interface, trading controls, and settings.
Includes state management with Zustand, API integration with
Axios/TanStack Query, and interactive charts with Recharts.

frontend/.gitignore

@@ -0,0 +1,26 @@
+# Dependencies
+node_modules/
+dist/
+
+# Logs
+*.log
+npm-debug.log*
+
+# Environment
+.env
+.env.local
+.env.*.local
+.env.production
+!.env.example
+!.env.template
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db