Lower finished threshold from 90% to 75%

Applies to frontend player, backend safety net, and stats display.

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

frontend/src/components/VideoPlayer.jsx

@@ -158,7 +158,7 @@ export default function VideoPlayer() {
     saveTimerRef.current = setTimeout(() => {
       if (video?.id) {
         const duration = video.duration_seconds ?? 0;
-        const watched = duration > 0 && secs >= duration * 0.9;
+        const watched = duration > 0 && secs >= duration * 0.75;
         updateProgress(video.id, { watch_progress_seconds: secs, watched });
       }
     }, 10_000);

frontend/src/pages/Stats.jsx

@@ -87,7 +87,7 @@ export default function Stats() {
         <StatCard
           label="Finished"
           value={(data.finished_count || 0).toLocaleString()}
-          sub="watched ≥90%"
+          sub="watched ≥75%"
         />
         <StatCard
           label="Bailed early"