Fix library thumbnails and let clips keep a display name.

Extract a poster frame when a still-thumb is missing, and show the clip name in the library with the prompt on the info icon.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/api/library/clips/[id]/video.get.ts

@@ -10,7 +10,7 @@ export default defineEventHandler((event) => {
     throw createError({ statusCode: 404, statusMessage: 'Video file is missing' })
   }
   setHeader(event, 'Content-Type', 'video/mp4')
-  setHeader(event, 'Content-Disposition', `inline; filename="${clip.id}.mp4"`)
+  setHeader(event, 'Content-Disposition', `inline; filename="${safeDownloadName(clipTitle(clip))}.mp4"`)
   setHeader(event, 'Cache-Control', 'private, max-age=3600')
   return readFileSync(path)
 })