docs: add Security Center, Billing, and Leaderboard comprehensive documentation and summary guides

docs/README.md

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+
+---
+
+## 📋 Security, Billing & Leaderboard Documentation
+
+This directory contains comprehensive documentation for three core New-API modules:
+
+### Available Reports
+1. **[SECURITY_BILLING_LEADERBOARD_REPORT.md](./SECURITY_BILLING_LEADERBOARD_REPORT.md)** - Full technical documentation (887 lines)
+   - Detailed security center architecture and features
+   - Complete billing system design and implementation
+   - Leaderboard functionality and integration points
+   - API endpoints, data models, and best practices
+   - Troubleshooting and extension guidelines
+
+2. **[SECURITY_BILLING_LEADERBOARD_SUMMARY.md](./SECURITY_BILLING_LEADERBOARD_SUMMARY.md)** - Quick reference guide (234 lines)
+   - Quick API lookup tables
+   - Core concepts and configuration
+   - Common troubleshooting
+   - Resource links
+
+### Key Topics
+
+#### 🔒 Security Center
+- Violation detection and recording
+- User ban management
+- Model redirection configuration
+- Automatic ban mechanism
+- Dashboard statistics
+
+#### 💰 Billing System
+- Token counting and quota management
+- Top-up (recharge) functionality
+- Payment gateway integration (EPay, Stripe)
+- Subscription plans
+- Voucher system
+- New Billing Engine architecture
+
+#### 🏆 Leaderboard
+- User statistics and rankings
+- Multi-window time support
+- Token IP usage tracking
+- Performance optimization
+
+### Quick Links
+- [Full Report](./SECURITY_BILLING_LEADERBOARD_REPORT.md)
+- [Quick Reference](./SECURITY_BILLING_LEADERBOARD_SUMMARY.md)
+
+---