Add GetNotebook RPC for pulling complete notebook data

New RPC returns notebook metadata, all pages, and all strokes for
a given server-side notebook ID. Enables desktop and other clients
to download notebooks from the server (pull sync).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/grpcserver/sync.go

@@ -114,6 +114,71 @@ func (s *SyncService) SyncNotebook(ctx context.Context, req *pb.SyncNotebookRequ
 	}, nil
 }
 
+func (s *SyncService) GetNotebook(ctx context.Context, req *pb.GetNotebookRequest) (*pb.GetNotebookResponse, error) {
+	userID, ok := UserIDFromContext(ctx)
+	if !ok {
+		return nil, status.Error(codes.Internal, "missing user context")
+	}
+
+	var resp pb.GetNotebookResponse
+	var syncedAt int64
+	err := s.DB.QueryRowContext(ctx,
+		"SELECT id, remote_id, title, page_size, synced_at FROM notebooks WHERE id = ? AND user_id = ?",
+		req.NotebookId, userID,
+	).Scan(&resp.ServerNotebookId, &resp.RemoteId, &resp.Title, &resp.PageSize, &syncedAt)
+	if err == sql.ErrNoRows {
+		return nil, status.Error(codes.NotFound, "notebook not found")
+	}
+	if err != nil {
+		return nil, status.Errorf(codes.Internal, "query notebook: %v", err)
+	}
+	resp.SyncedAt = timestamppb.New(time.UnixMilli(syncedAt))
+
+	pageRows, err := s.DB.QueryContext(ctx,
+		"SELECT id, remote_id, page_number FROM pages WHERE notebook_id = ? ORDER BY page_number",
+		resp.ServerNotebookId,
+	)
+	if err != nil {
+		return nil, status.Errorf(codes.Internal, "query pages: %v", err)
+	}
+	defer func() { _ = pageRows.Close() }()
+
+	for pageRows.Next() {
+		var pageID, remoteID int64
+		var pageNum int32
+		if err := pageRows.Scan(&pageID, &remoteID, &pageNum); err != nil {
+			return nil, status.Errorf(codes.Internal, "scan page: %v", err)
+		}
+
+		pd := &pb.PageData{
+			PageId:     remoteID,
+			PageNumber: pageNum,
+		}
+
+		strokeRows, err := s.DB.QueryContext(ctx,
+			"SELECT pen_size, color, style, point_data, stroke_order FROM strokes WHERE page_id = ? ORDER BY stroke_order",
+			pageID,
+		)
+		if err != nil {
+			return nil, status.Errorf(codes.Internal, "query strokes: %v", err)
+		}
+
+		for strokeRows.Next() {
+			var sd pb.StrokeData
+			if err := strokeRows.Scan(&sd.PenSize, &sd.Color, &sd.Style, &sd.PointData, &sd.StrokeOrder); err != nil {
+				_ = strokeRows.Close()
+				return nil, status.Errorf(codes.Internal, "scan stroke: %v", err)
+			}
+			pd.Strokes = append(pd.Strokes, &sd)
+		}
+		_ = strokeRows.Close()
+
+		resp.Pages = append(resp.Pages, pd)
+	}
+
+	return &resp, nil
+}
+
 func (s *SyncService) DeleteNotebook(ctx context.Context, req *pb.DeleteNotebookRequest) (*pb.DeleteNotebookResponse, error) {
 	userID, ok := UserIDFromContext(ctx)
 	if !ok {