feat: add security system with system-wide proxy, DNS protection and encryption

- System-wide proxy: automatic Windows proxy configuration for all apps
- DNS leak protection: force all DNS queries through VPN
- Config encryption: AES-256-GCM encryption for all config files
- File protection: strict access permissions for config directory
- Leak detection: built-in security check system
- Kill Switch: temporarily disabled (will be improved in next version)

Security features:
✓ Automatic system proxy setup
✓ DNS leak protection (optional)
✓ AES-256-GCM config encryption
✓ File and directory protection
✓ Security leak checker
⚠ Kill Switch disabled (caused internet blocking issues)

Emergency recovery scripts included:
- ОТКЛЮЧИТЬ_KILLSWITCH.bat
- EMERGENCY_FIX_INTERNET.bat
- ЕСЛИ_СЛОМАЛСЯ_ИНТЕРНЕТ.txt

Documentation:
- Markdown/SECURITY_GUIDE.md - full security guide
- БЕЗОПАСНОСТЬ_БЫСТРЫЙ_СТАРТ.md - quick start guide
- CHANGELOG_SECURITY.md - detailed changelog

.gitignore

@@ -7,6 +7,10 @@ vpn-client.exe
 *.dylib
 *.bat
 *.sh
+init.bat
+init.sh
+build.bat
+build.sh
 
 # Test binary
 *.test