Add options that define when preview builds get destroyed

**Is your feature request related to a problem? Please describe.**
We have a process were a certain pr is merged and then processed by the QA team.
The problem is that after a pr is merged you can no longer see the preview link so the QA team cannot access it.

**Describe the solution you'd like**
I would like to have the option to keep the preview link after the pr merges. Or better have the option to decide when preview links should be destroyed. Some options could be:
- Destroy preview link when pr merges
- Destroy preview link when branch is deleted
- Destroy preview link when pr is closed
- Never destroy preview link. (You can always destroy the links manually from the console)

**Additional context**
Add any other context or screenshots about the feature request here.

No implementation files, tests, or entry points are identified in the issue. Start by locating the preview-build cleanup flow and trace what happens when a pull request merges, closes, or its branch is deleted. Done means the configured destruction condition is honored, including the option to retain links indefinitely and manual console deletion remains available.

Written by the indexing model from the issue text.