Reduce codebase by implementing top five refactoring

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 :)

Round nine of the reduction sweep: every duplication scan on the 1.1M-line tree came back near zero, so the one window the fleet census closed was retired (DBOS retired-name adoption, −70 lines; PR #7418 queued to the lane). Four ranked opportunities named with their open gates; Terraform module extraction (~2,000 dup lines) deferred as a follow-up. Quick gate green; 80 touched API tests green; blind review pass; no UI surface affected.