Identify and implement code reduction opportunities

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 16: four cuts, net −470 lines (+281/−751, 26 files): retired the inert Jarvis *_write switches and their permission grid, host rename in place on a shared EditableRow, always-true ProjectEditPage guards, three caller-less API functions. Quick gate green; 448 API + 930 web tests green; code/security/verifier lanes pass; PR #7867 queued to the merge lane. Deferred: older-node shim retirement (cp-psql credential refused). Visual check done on Settings and host page, both clean. Memory: used mem-25288/35380/32882/31277/31548; proposed 0.