Enhance GitLeaks Security Implementation

[manideepk90]

1. Improve GitLeaks Configuration
   • Add more specific secret patterns for payment industry
   • Add custom rules for API keys, tokens, and credentials
   • Enhance allowlists with more precise regex patterns
2. Add GitLeaks to Package.json Scripts
3. Create Documentation for Security Practices
4. Add Secret Scanning for Environment Variables if missed in gitignore