Identify and implement top 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 :)

Measured every reduction axis at wider thresholds: the tree is at its mechanical floor (0 dead symbols, 2 dead routes/30 lines, 1 of 187 deletable tests). Implemented the safe remainder: 15 folds across web, api and jaahd, net -181 lines; blind review lanes caught and fixed one NodeVault lock regression. PR #7822 queued to the merge lane. Large remaining candidates (older-CP shims, NodeGroup dialog) are decisions, named in the report.