The service worker uses staleWhileRevalidate on /dist/*, so after a
release it would serve old bundles from cache indefinitely (cache is
only wiped when the cache *name* changes, which was hardcoded to
'dashcaddy-shell-v10'). Result: dashboard appears unchanged after a
self-update until the user manually unregisters the SW.
build.js now hashes the concatenated dist bundles and writes
`dashcaddy-shell-<10-hex-chars>` into sw.js. Any change in dist/
produces a fresh cache name; on the next page load the SW's activate
handler deletes all older caches and the new bundles are fetched.