Fix comments (Python API), add dislike bar

Comments: switch from CLI --write-comments to yt-dlp Python API with
getcomments=True — more reliable, proper extractor_args dict format

Dislikes: add dislike_count column, fetch from returnyoutubedislike.com
after each video metadata upsert (5s timeout, non-fatal)

UI: replace emoji like count with a like/dislike ratio bar — blue fill
showing like proportion, labels on each end; views stay in meta row

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

backend/routers/videos.py

@@ -67,6 +67,7 @@ class VideoDetail(BaseModel):
     is_recommended: bool = False
     view_count: Optional[int] = None
     like_count: Optional[int] = None
+    dislike_count: Optional[int] = None
 
     model_config = {"from_attributes": True}
 
@@ -423,7 +424,7 @@ def surprise_me(
 
 _VIDEO_SELECT = """
     SELECT v.id, v.youtube_video_id, v.title, v.description, v.thumbnail_url,
-           v.duration_seconds, v.published_at, v.tags, v.category, v.view_count, v.like_count,
+           v.duration_seconds, v.published_at, v.tags, v.category, v.view_count, v.like_count, v.dislike_count,
            c.id AS channel_id, c.name AS channel_name, c.youtube_channel_id AS channel_youtube_id,
            COALESCE(uv.watched, 0) AS watched,
            COALESCE(uv.watch_progress_seconds, 0) AS watch_progress_seconds,
@@ -488,6 +489,12 @@ def _upsert_video_from_yt(db: Session, youtube_video_id: str) -> bool:
         if channel:
             video.channel_id = channel.id
 
+    # Fetch crowdsourced dislike count if not already known
+    if not video.dislike_count:
+        dislikes = ytdlp.fetch_dislike_count(youtube_video_id)
+        if dislikes is not None:
+            video.dislike_count = dislikes
+
     db.commit()
     return True