ui: video cards were missing the mimetype accent

Videos.js has its own VideoCard, separate from the file cards in Files.js, so
restoring the accent there missed it -- archives and documents showed the edge
and videos did not.

Audited every remaining `<Card>` rather than fixing the one that was reported.
The only two without an accent are the map's place card and the loading
placeholder, and neither has a mimetype to colour, so both are correct.

Videos show blue and audio-only entries show violet, which is right rather than
inconsistent: both come from `mimetypeColor`, the same helper that colours the
file icons, so a card and its icon can never disagree.

app/src/components/Videos.js

@@ -15,6 +15,7 @@ import {
     HelpHeader,
     InfoHeader,
     isoDatetimeToAgoPopup,
+    mimetypeColor,
     PageContainer,
     PreviewLink,
     scrollToTop,
@@ -880,7 +881,8 @@ export function VideoCard({file}) {
         <div>{detailLine}</div>
     </>;
 
-    return <Card media={media} title={titleElm} meta={meta}/>
+    return <Card media={media} title={titleElm} meta={meta}
+                 color={mimetypeColor(file.mimetype, file.primary_path)}/>
 }
 
 export function VideoRowCells({file}) {