Expose last evaluated datetime for flags

[khvn26]

Is your feature request related to a problem? Please describe.

Currently, stale flags are determined based solely on creation date. While it can be helpful, using the date of last evaluation is more correct.

Describe the solution you'd like.

Store the date of last evaluation for each feature state. Expose it in the UI. Extend workflows stale flags logic to use it, if available.

Describe alternatives you've considered

N/A

Additional context

No response