Improve Temporal Place Hierarchy Management

[Ziesie1]

Gramps Web currently allows assigning a place to a higher-level location for a specific time period (e.g. Celle belonging to Landkreis Celle between certain years). However, once this hierarchy is created, it cannot be edited, and the time period is not visible anywhere in the UI.

This makes it difficult to manage historical accuracy, especially when administrative boundaries change over time.

Suggested improvements:

• Allow users to edit existing place hierarchy relationships, including the time period.
• Display the assigned time period in the place hierarchy view.

Thanks for your great work on Gramps Web!