[Feature Request]: start2end video

### Is there an existing issue for this?

- [x] I have searched the existing issues and checked the recent builds/commits

### What would your feature do ?

Is this possible to add start and end frames images as inputs?

### Proposed workflow

1. Go to ....
2. Press ....
3. ...

### Additional information

_No response_

### Are you going to help adding it?

no

The issue mentions adding start and end frame images as inputs but names no files, tests, or entry points. Begin by tracing the existing animation and video input workflow, then define how the two frame inputs should behave. Done means the proposed workflow is specified and the feature works with both start and end frame images.

Written by the indexing model from the issue text.