Add Metrics page

As of now metrics are only logged via journal entries. Add a page that allows users to add or edit metrics to remove clutter from the journal.

There should be some way to identify which Metrics are coming from a journal entry. If a metric came from a journal entry do not allow the user to edit or delete that metric outside of the journal entry. In this case, link to the journal entry in the Metrics view.

Start by reading how metrics are currently logged through journal entries and how the journal view is structured. Define the Metrics page behavior, including identifying journal-sourced metrics, preventing edits or deletion for those metrics, and linking them back to the journal entry.

Written by the indexing model from the issue text.