Page title needs more top margin

I tested the change locally and compared the result with the original screenshot. The page title now has better spacing at the top and looks more balanced.

Increasing the top margin to `var(--admin-space-m)` seems to work well. The existing bottom margin is unchanged, so the spacing below the title is maintained.

I didn't notice any layout issues during my testing, and the change looks good to me.

One small suggestion: the MR title mentions padding, but the actual change is to the margin. It would be good to update the title for clarity.

The Needs Review Queue Bot tested this issue. It fails the Drupal core commit checks. Therefore, this issue status is now "Needs work".

This does not mean that the patch necessarily needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

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Thanks for the automated test report. I checked the failure and found that the compiled CSS was not in sync with the source CSS file.

I've rebuilt the CSS using `yarn run build:css` and pushed the updated changes to the issue fork.

The other checks, including CSpell, PHPStan and Stylelint, were already passing. I'll check the updated test results once the bot runs again.