Closes #135

🔧 Key Features Implemented

• JWT Token Generation: Creates secure tokens with user_id and role claims
• Token Verification: Validates JWT tokens and extracts user information
• Route Protection: Middleware protects sensitive endpoints (/kyc/, /wallet/)
• WebAuthn Integration: Mock WebAuthn verification (ready for real implementation)
• Comprehensive Testing: Unit tests cover all functionality with mocking
• Environment Security: JWT_SECRET validation with minimum length requirements
• Error Handling: Proper HTTP status codes and error messages

🚀 API Endpoints

• POST /auth/login: Authenticates users and returns JWT tokens
• Protected Routes: All /kyc/* and /wallet/* routes now require valid JWT tokens

🧪 Testing Coverage

• JWT token generation and verification
• Middleware functionality with various scenarios
• Login endpoint with success and error cases
• WebAuthn verification mocking
• Proper error handling and status codes

🔒 Security Features

• JWT tokens expire in 24 hours
• Bearer token authentication
• Environment variable validation
• Secure token signing with HS256 algorithm
• Input validation for all endpoints