add dynamic default transition time option for Light Component

[karol27]

Component name

light

Link to component documentation on our website

https://esphome.io/components/light/

Describe the enhancement

There was a previous PR (#7717 by @NewoPL) adding dynamic_default_transition support for light.
It was automatically closed due to inactivity, but the feature worked and was confirmed functional by several users.

Would it be possible to reopen or continue that PR?
I’d be happy to test and help maintain it if needed.

Original PR: esphome/esphome#7717

Use cases

The current default_transition_length behavior works well for full on/off transitions (from 0% to 100% brightness or vice versa).
However, when only a small brightness change occurs — for example, from 80% to 90% — the same transition time is applied, which makes the change appear unnecessarily slow and unnatural.

Adding a dynamic transition mechanism (e.g. dynamic_default_transition) would allow the transition duration to scale based on the actual brightness difference.
This would make light fading smoother and more realistic in daily use while keeping the long transitions for full fades.

Anything else?

No response

[github-actions[bot]]

🏷️ I've automatically added the component: light label to help categorize this feature request.