Track video clicks as engagement signals

- stats: started_count now includes any video opened (last_watched_at set)
  not just ones with saved progress seconds
- VideoPlayer: fires updateProgress immediately on open so even a
  click-and-back sets last_watched_at and counts as a started video

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/stats.py

@@ -140,7 +140,7 @@ def get_stats(
         text("""
             SELECT COUNT(*) AS n FROM user_videos
             WHERE user_id = :uid AND watched = 0
-              AND watch_progress_seconds > 0
+              AND (watch_progress_seconds > 0 OR last_watched_at IS NOT NULL)
         """),
         {"uid": uid},
     ).mappings().first()

frontend/src/components/VideoPlayer.jsx

@@ -126,6 +126,16 @@ export default function VideoPlayer() {
     }
   }, [dlStatus?.status]); // eslint-disable-line react-hooks/exhaustive-deps
 
+  // Record a "clicked" impression as soon as we have the video id — even if the
+  // user closes immediately before playback starts.
+  const clickedRef = useRef(false);
+  useEffect(() => {
+    if (video?.id && !clickedRef.current && !video.is_watched) {
+      clickedRef.current = true;
+      updateProgress(video.id, { watch_progress_seconds: video.watch_progress_seconds ?? 0 });
+    }
+  }, [video?.id]); // eslint-disable-line react-hooks/exhaustive-deps
+
   // ── Trigger download on open ──────────────────────────────────────────────
   const downloadMut = useMutation({
     mutationFn: (ytId) => createDownload(ytId),