The old service-worker.js (repo root, removed when web/ was rewritten)
cached every same-origin GET keyed only by frontend PACKAGE_VERSION, so
a backend-only change never invalidated it. Browsers that had visited
this origin before the rewrite kept getting stale cached API responses
(bootstrap/session calls) served instead of hitting the real backend --
looked like "login succeeds then immediately bounces back to login".
Adds a same-path kill-switch service-worker.js that purges all caches
and unregisters itself, plus an explicit update() check on app boot so
already-registered browsers don't have to wait for the browser's own
lazy update schedule.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
