Identify and implement top 5 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 :)

Swept the whole tree (dead code, window census, legacy markers, UI duplicates): nothing dead or textually twinned left. Folded the 5 largest structural twins (login door suites, vendor-wave harness, production QA readers, cloud-lifecycle pair, web fixtures): net −399 lines over 40 files, 1,511 API + 61 web tests green, quick gate green. PR #7952 queued to the merge lane. Assumed "any part of the repo" includes tests (where the duplication is). Deferred: legacy alias mount, git_credential_id pointer, writer-dead readers (cp_psql refused), e2e preludes (no Playwright here). Memory: used mem-25288; proposed 1 gotcha.