[backport cloud/1.42] fix: use server response filename in WebcamCapture serialization (#10220) (#10904)

Backport of #10220 to cloud/1.42. Clean cherry-pick.

Co-authored-by: Deep Mehta <42841935+deepme987@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/extensions/core/webcamCapture.ts

@@ -142,7 +142,10 @@ app.registerExtension({
         useToastStore().addAlert(err)
         throw new Error(err)
       }
-      return `webcam/${name} [temp]`
+      const data = await resp.json()
+      const serverName = data.name ?? name
+      const subfolder = data.subfolder ?? 'webcam'
+      return `${subfolder}/${serverName} [temp]`
     }
 
     // @ts-expect-error fixme ts strict error