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 :)

Implemented the five best verified code reductions (net −590 lines, 20 files): deleted unreferenced tools/perf scripts; folded SignupActivatingPage into SignupWelcomePage; one useLinkCodeFlow hook behind Slack/Telegram connect; one mountinfo reader in jaahd shared_storage; shared email/Telegram notify drivers. Repo-wide sweeps found 0.16 % duplication and no dead code, so "massive" was not available (evidence in report). Quick gate green, review lane pass, PR #6881 merged by the lane, Jaah Deploy succeeded. Deferred follow-ups named in the PR. Visual check done on signup pages. Memory: used mem-25288; proposed 0.