fix: téléchargement et progression

- Format yt-dlp corrigé : Arte sert l'audio en mp4 pas m4a, l'ancien
  sélecteur échouait immédiatement avec ExtractorError
- Progression basée sur downloaded_bytes/total_bytes_estimate (plus
  fiable pour HLS que _percent_str)
- finished_once : empêche le flux audio de remettre la progression à 0%
  après que le flux vidéo soit terminé

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

downloader.py

@@ -86,26 +86,30 @@ class DownloadManager:
         with _db() as conn:
             conn.execute("UPDATE downloads SET state='downloading' WHERE id=?", (dl_id,))
 
+        # For HLS, yt-dlp downloads video then audio separately.
+        # After the first stream finishes, stay in "processing" — don't reset
+        # to "downloading" when the audio stream starts.
+        finished_once = [False]
+
         def hook(d):
-            if d["status"] == "downloading":
-                raw = d.get("_percent_str", "0%").strip().rstrip("%")
-                try:
-                    pct = float(raw)
-                except ValueError:
-                    pct = 0.0
+            if d["status"] == "downloading" and not finished_once[0]:
+                dl = d.get("downloaded_bytes") or 0
+                total = d.get("total_bytes") or d.get("total_bytes_estimate") or 0
+                pct = min(dl / total * 100, 99.0) if total > 0 else 0.0
                 self._set(
                     dl_id,
                     state="downloading",
-                    progress=pct,
+                    progress=round(pct, 1),
                     speed=d.get("_speed_str", ""),
                     eta=d.get("eta"),
                 )
             elif d["status"] == "finished":
+                finished_once[0] = True
                 self._set(dl_id, state="processing", progress=100)
 
         ydl_opts = {
             "outtmpl": f"{OUTPUT_DIR}/%(title)s.%(ext)s",
-            "format": "bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best",
+            "format": "bestvideo[vcodec^=avc1]+bestaudio/bestvideo+bestaudio/best",
             "merge_output_format": "mp4",
             "progress_hooks": [hook],
             "quiet": True,