The view linked to /assets/<assetid>, which is not a route. Each asset type
has its own detail route keyed by its own id (/machines/<machineid>), and
there is no generic asset detail page to return to, so the link 404'd.
Uses router.back() instead: this page is only ever reached from an asset
panel, so history is the correct destination regardless of the asset type,
and it needs no per-type route table. Falls back to the machines list when
opened directly from a pasted URL.
The /api/assets/<id> call that fetches the heading name is unaffected - that
endpoint does exist; it was only the frontend route that did not.
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