Security: Fix critical vulnerabilities and implement security hardening

CRITICAL SECURITY FIXES:
- Fixed certificate validation bypass vulnerability in BTCPayServerService
  * Removed unsafe ServerCertificateCustomValidationCallback
  * Added environment-specific SSL configuration
  * Production now enforces proper SSL validation

- Fixed overly permissive CORS policy
  * Replaced AllowAnyOrigin() with specific trusted origins
  * Created separate CORS policies for Development/Production/API
  * Configured from appsettings for environment-specific control

- Implemented CSRF protection across admin panel
  * Added [ValidateAntiForgeryToken] to all POST/PUT/DELETE actions
  * Protected 10 admin controllers with anti-forgery tokens
  * Prevents Cross-Site Request Forgery attacks

CONFIGURATION IMPROVEMENTS:
- Created appsettings.Development.json for dev-specific settings
- Added Security:AllowInsecureSSL flag (Development only)
- Added CORS:AllowedOrigins configuration arrays
- Created comprehensive security roadmap (ROADMAP.md)

ALSO FIXED:
- TeleBot syntax errors (Program.cs, MessageFormatter.cs)
- Added enterprise-full-stack-developer output style

Impact: All Phase 1 critical security vulnerabilities resolved
Status: Ready for security review and deployment preparation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -184,11 +184,15 @@ The API is built with:
 - Self-hosted payment processing
 - GDPR-friendly design (minimal data collection)
 
-## Future Enhancements
+## Development Roadmap
 
-- Royal Mail API integration for shipping
-- Email notifications
-- Inventory management
-- Multi-currency pricing
-- Advanced reporting
-- Order export functionality# Test push after proxy update
+See [ROADMAP.md](./ROADMAP.md) for detailed development plans, including:
+- 🚨 Critical security fixes (immediate priority)
+- 📋 Production readiness improvements
+- 🚀 Feature enhancements (shipping, notifications, analytics)
+- 🏗️ Long-term scalability and optimization plans
+
+## Recent Updates
+- Security vulnerabilities identified and documented (Sep 19, 2025)
+- BTCPay Server integration fixed with production credentials (Sep 19, 2025)
+- Product variations and mobile workflow implemented (Sep 18, 2025)