feat(Model): #1028 made model.json optional

[namchuai]

Describe Your Changes

• model.json will be generated if not exist when app start

Fixes Issues

• fixes #1028 #1196

Self Checklist

• [ ] Added relevant comments, esp in complex areas
• [ ] Updated docs (for bug fixes / features)
• [ ] Created issues for follow-up changes or refactoring needed