feat: cortex models delete command

[vansangpfiev]

Describe Your Changes

Support cortex models delete command CLI syntax:

cortex models delete <model_id>

Server API:

DELETE http://127.0.0.1:3928/models/model_id

Fixes Issues

• Closes https://github.com/janhq/cortex.cpp/issues/1064

Self Checklist

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

[namchuai]

Would be great if we have some e2e tests 👯

[vansangpfiev]

Would be great if we have some e2e tests 👯

Added e2e tests