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 :)

Identified the top 5 line-count reductions and shipped them: doctrine bundles from one key table, 16 hand-rolled 404s onto or_404, one getBlob for attachment reads, Efficiency sessions on FeedList, shared test helpers. Net −172 lines; quick gate green; PR #7718 queued to the merge lane. Massive cuts need product decisions (legacy runtime, record dialogs), named as deferred in the report.