Implement Massive Repository Code Reduction

Identify an opportunity 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 - Front end component or group of them duplicates another component functionality. Use the most modern and nice looking - Move to DBOS and get rid of supporting functionality relying on DBOS - etc. Implement it

Net −796 lines with zero behaviour change: cron system-cadence wrappers collapsed (−342) plus single-homed api test doubles and census helpers. Gate green, PR #5239 merged, Jaah Deploy succeeded. Deferred: get_or_404 adoption, paged() helper, react-query migration.