Identify and implement top five code reduction

Identify top 5 opportunities to massively reduce the amount of code (lines of code) in any part of the repo: - Similar functionality that can be unified and reused - Code that has been valuable but no more - A front end component or a group of them duplicate another component/page functionality. Use the most modern and nice looking - etc. Now implement them :)

Merge-lane re-dispatch fixed: mirror-trees-strict and community-edition-tooling-suite both failed on cron_retention.py importing app.dmarc under a None check; restored the edition_features.enabled("system_mail") guard the tree checker reads. Lanes green locally, retention suite 51 passed, quick gate pass. Rebased, pushed 45ffea1c27, PR #7722 re-queued to the lane. No UI surface affected. Memory: none applied.