How long will this actually take?

I want to build: <describe the feature>
My guess is: <your estimate>

Break it into tasks and estimate each. Then add the things I've almost
certainly forgotten:
- Error states, empty states, loading states.
- Validation, on both sides.
- The mobile layout.
- Testing it myself, properly.
- Deploying it and finding out what differs in production.

Give me a realistic total, and tell me which single task carries the
most uncertainty.

If my guess is badly out, say so and say why.