Reduce codebase by implementing top five refactoring

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 5 code-reduction refactorings in 6 commits (net −215 lines; −284 outside tests): API Out models via from_row (−311), credential testers raise a verdict (−60), web TabbedPanels / TimeSeriesPlot / useServerDraft+useBaselineDirty unifications (line-neutral: +34/+30/+23, duplicated mechanisms removed). Quick gate, 12,386 web tests, 28,777 API tests green (1 order-dependent failure passes alone, outside the diff). Visual check done at desktop and phone: tabbed pages, dashboard, settings editors render as before; chart surfaces had no live data, covered by component tests. Deferred: tools/check.sh stage discovery and 15 never-run tools/tests suites. PR #7413 queued to the merge lane.