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 :)

Resumed: first attempt had opened PR #7881 (net −510 lines, 143 files: route wrappers onto @on_session, one forge HTTP path, one session-epoch retire helper, Tasks board rosters on react-query, test purges on shared fixtures) but never reported it. Re-ran quick gate (pass, 28s) on the same head 2bb326e5, uploaded the report, enqueued the PR; lane answered queued. Visual check on the Tasks board done in attempt 1 (readable, nothing clipped). Larger cuts needing owner decisions named in the report. Memory: used mem-25288, mem-32882, mem-35754; proposed none.