Feature Request: Default Life Span Configuration or Keyboard Shortcut for Video Annotations

**Is your feature request related to a problem? Please describe.**
Hello, the software is great and we are deciding if use or not in our organization.

Most of our projects are about annotating long videos frame-by-frame with each class present in only one single frame. Every annotation defaults to a life span covering the entire video. I need to manually click a button to set the life span to 0 for each annotation, which becomes impractical with hundreds of single-frame annotations.

**Describe the solution you'd like**
Add a configuration option to set the default life span to 0 (single frame) for video annotations, either through:

A parameter in the labeling config template (e.g., defaultLifespan="0")
A keyboard shortcut to quickly reset life span to 0
A project-level setting

**Additional context**
This is the button I'm referring to:

This would significantly improve workflow efficiency for frame-by-frame video annotation tasks where objects appear only in specific frames.

Thank you for your help!