Suggestion: Upgrade Tailwind to v4

### What problem do you want to solve?

The project is using an older Tailwind version and is missing v4 improvements and compatibility with its current ecosystem.

### What do you think is the correct solution?

Upgrade Tailwind and related tooling to v4.

### Participation

- [x] I am willing to submit a pull request for this change.

### AI acknowledgment

- [x] I did not use AI to generate this issue report.
- [ ] (If the above is not checked) I have reviewed the AI-generated content before submitting.

### Additional comments

_No response_