feat(auth): implement WhatsApp OTP sending function for login

- Create sendCodeOtp utility function using otp.wibudev.com API
- Update login route to use new sendCodeOtp function
- Replace old URL-based WhatsApp approach with authenticated API call
- Add WA_SERVER_TOKEN environment variable documentation
- Support flexible codeOtp type (string | number) for better reusability

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

.env.example

@@ -11,6 +11,9 @@ SEAFILE_PUBLIC_SHARE_TOKEN=your_seafile_public_share_token
 WIBU_UPLOAD_DIR=uploads
 WIBU_DOWNLOAD_DIR=./download
 
+# WhatsApp Server Configuration
+WA_SERVER_TOKEN=your_whatsapp_server_token
+
 # Application Configuration
 # IMPORTANT: For staging/production, set this to your actual domain
 # Local development: NEXT_PUBLIC_BASE_URL=http://localhost:3000