Top 5 code reduction opportunities for repository

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Measured the whole tree (1.65M lines): duplication 0.02–0.04%, dead code ~0.01%, no superseded page/module/tool — no massive code-only reduction exists. Ranked top 5 with sizes; implemented the one pure cleanup (dead web mirrors + their parity-guard arms, −134 lines) in PR #7425, review lane pass ×3, quick gate green, queued to the merge lane. Deferred: owner decision on six never-used subsystems (~49k lines, prod has 0 rows), OpenAPI-generated types.ts (3.3k). Visual check: no UI surface affected. Memory: used mem-31005; proposed 1 gotcha (mem-31300).