Preview URLs now carry a cache-busting `&v=<mtime_ns>` suffix, so the media
type could no longer be read from the end of the string. Model cards,
duplicates, recipe cards and modals, the showcase thumbnail and the ComfyUI
preview tooltip all fell into the image branch and rendered `<img>` for video
previews, which browsers cannot decode.
Move the query-aware video detection that already lived in the versions tab
into a shared mediaTypes helper and use it everywhere a server-provided
preview URL is inspected. The web UI and the ComfyUI widget bundle each keep a
copy because they are served from different mounts. Video previews that turn
out to be webm now also get the right `<source type>`.
Add regression coverage for versioned mp4/webm/image URLs.
Fixes#1168
Will Miao
14e90006de