docs: clarify local setup for update_metricsDocs/update metrics local setup

[keranbyge]

While investigating issue #2359, I ran into the same
"permission denied for table ticket" error when running
update_metrics locally.

This PR documents the required local setup steps
(database creation, Trac schema import, and permissions)
to ensure update_metrics runs successfully.

Fixes #2359

[ulgens]

High level issues:

• Please install pre-commit hooks locally, using prek install. Then you can run the hooks againist all files using prek run --all-files and you'll see a failure.
• Please only include the related commit.

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Coming from

This seems like a documentation / setup gap rather than a code bug. I’d be happy to open a PR to clarify the local setup steps if that would be helpful.

#2359 (comment)

I was expecting this PR to be an update in Setting up database access section. I'm not sure a new section is needed.

[keranbyge]

Thanks for the review!

I’ve now:

Installed and verified the pre-commit hooks locally (CI is passing).

Cleaned up the PR so it only includes the relevant documentation change.

Moved the update_metrics local setup details into the existing “Setting up database access” section instead of introducing a new section.

Please let me know if this looks good or if you’d prefer the guidance structured differently.

[ulgens]

I'm missing why you deleted the readme. Also, please try to use rebasing to update your branch, not "merge 'main' into <your_branch>" approach. Rebase yields a much cleaner diff and git history.