Implement a way for admins to introduce new weeks and set them as the last active one.
The last active week is the last one that is accessible to players, and will also prevent
the graph from being displayed.
Implement arrows for navigating between the weeks in the HTML.
- Create a new migration adding a Weeks table, allowing for new weekly introductions
and paving the way for multiple week handling.
- Add route to update the weekly introduction
- Move the week rendering to a specific week file
- Update the templates to use the week number from the week data
- Update templates to render and edit weekly introductions
