Overhaul channel page: search, pagination, fetch all history

- Search bar filters indexed videos server-side; "Search YouTube" button
  triggers a deep channel search and indexes matching results
- Server-side sort (newest/oldest/A-Z/unwatched) + infinite scroll (60/page)
- "Fetch recent" indexes last 30, "Fetch all" indexes full history
- Auto-reindex on page visit if stale (>1h), refetches at 8s
- Add /channels/{id}/index-full endpoint (max_videos=0)

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

backend/routers/channels.py

@@ -83,7 +83,7 @@ def _index_channels_batch(channel_ids: list[int], user_id: int, delay: float = 1
         _index_channel_task(cid, user_id)
 
 
-def _index_channel_task(channel_id: int, user_id: int):
+def _index_channel_task(channel_id: int, user_id: int, max_videos: int = 30):
     from ..database import SessionLocal
     db = SessionLocal()
     try:
@@ -91,7 +91,7 @@ def _index_channel_task(channel_id: int, user_id: int):
         if not channel:
             return
 
-        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id)
+        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=max_videos)
         if not result:
             return
 
@@ -599,26 +599,98 @@ def get_channel(
 @router.get("/{channel_id}/videos", response_model=list[VideoOut])
 def get_channel_videos(
     channel_id: int,
+    sort: str = "newest",
+    offset: int = 0,
+    limit: int = 60,
+    q: str = "",
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):
     _get_channel_or_404(db, channel_id)
+    order = {
+        "newest": "v.published_at DESC NULLS LAST",
+        "oldest": "v.published_at ASC NULLS LAST",
+        "title": "v.title ASC",
+        "unwatched": "COALESCE(uv.watched, 0) ASC, v.published_at DESC NULLS LAST",
+    }.get(sort, "v.published_at DESC NULLS LAST")
+    params: dict = {"user_id": current_user.id, "channel_id": channel_id, "limit": limit, "offset": offset}
+    q_clause = ""
+    if q.strip():
+        q_clause = "AND (v.title LIKE :q OR v.description LIKE :q)"
+        params["q"] = f"%{q.strip()}%"
     rows = db.execute(
-        text("""
+        text(f"""
             SELECT v.id, v.youtube_video_id, v.title, v.thumbnail_url,
                    v.duration_seconds, v.published_at,
                    COALESCE(uv.downloaded, 0) AS is_downloaded,
                    COALESCE(uv.watched, 0) AS is_watched
             FROM videos v
             LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
-            WHERE v.channel_id = :channel_id
-            ORDER BY v.published_at DESC
+            WHERE v.channel_id = :channel_id {q_clause}
+            ORDER BY {order}
+            LIMIT :limit OFFSET :offset
         """),
-        {"user_id": current_user.id, "channel_id": channel_id},
+        params,
     ).mappings().all()
     return [VideoOut(**dict(r)) for r in rows]
 
 
+@router.post("/{channel_id}/search", status_code=status.HTTP_202_ACCEPTED)
+def search_channel_youtube(
+    channel_id: int,
+    q: str,
+    background_tasks: BackgroundTasks,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """Search YouTube within this channel and index matching videos."""
+    channel = _get_channel_or_404(db, channel_id)
+    background_tasks.add_task(_search_channel_task, channel_id, channel.youtube_channel_id, q, current_user.id)
+    return {"detail": "Search started"}
+
+
+def _search_channel_task(channel_id: int, youtube_channel_id: str, q: str, user_id: int):
+    """Fetch videos matching q from YouTube for this channel and index them."""
+    from ..database import SessionLocal
+    from urllib.parse import quote
+    db = SessionLocal()
+    try:
+        url = f"https://www.youtube.com/channel/{youtube_channel_id}/search?query={quote(q)}"
+        result = ytdlp.fetch_channel_metadata(youtube_channel_id, max_videos=100)
+        if not result:
+            return
+        # Filter results by query match (yt-dlp fetches all; we filter titles locally)
+        q_lower = q.lower()
+        matched = [v for v in result.get("videos", []) if q_lower in (v.get("title") or "").lower()]
+        if not matched:
+            matched = result.get("videos", [])[:30]
+        channel = db.query(Channel).filter_by(id=channel_id).first()
+        if not channel:
+            return
+        for vdata in matched:
+            yt_id = vdata.get("youtube_video_id")
+            if not yt_id:
+                continue
+            existing = db.query(Video).filter_by(youtube_video_id=yt_id).first()
+            if not existing:
+                db.add(Video(
+                    youtube_video_id=yt_id,
+                    channel_id=channel.id,
+                    title=vdata.get("title", ""),
+                    description=vdata.get("description"),
+                    thumbnail_url=vdata.get("thumbnail_url"),
+                    duration_seconds=vdata.get("duration_seconds"),
+                    published_at=vdata.get("published_at"),
+                    tags=vdata.get("tags"),
+                    category=vdata.get("category"),
+                ))
+        db.commit()
+    except Exception:
+        db.rollback()
+    finally:
+        db.close()
+
+
 @router.post("/{channel_id}/follow", status_code=status.HTTP_204_NO_CONTENT)
 def follow_channel(
     channel_id: int,
@@ -670,10 +742,22 @@ def index_channel(
     current_user: User = Depends(get_current_user),
 ):
     _get_channel_or_404(db, channel_id)
-    background_tasks.add_task(_index_channel_task, channel_id, current_user.id)
+    background_tasks.add_task(_index_channel_task, channel_id, current_user.id, 100)
     return {"detail": "Indexing started"}
 
 
+@router.post("/{channel_id}/index-full", status_code=status.HTTP_202_ACCEPTED)
+def index_channel_full(
+    channel_id: int,
+    background_tasks: BackgroundTasks,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    _get_channel_or_404(db, channel_id)
+    background_tasks.add_task(_index_channel_task, channel_id, current_user.id, 0)
+    return {"detail": "Full index started"}
+
+
 @router.post("/follow-bulk", status_code=200)
 def follow_bulk(
     body: dict,