fix: regexp.DotAll flag in google engine and Metadata field removal

- google.go: use inline (?s) flag instead of regexp.DotAll second arg
- youtube.go: remove Metadata field (not in MainResult contract)
- config_test.go: fix expected engine count from 9 to 11 (google+youtube)

internal/engines/youtube.go

@@ -115,10 +115,6 @@ func (e *YouTubeEngine) Search(ctx context.Context, req contracts.SearchRequest)
 			Score:     1.0,
 			Category:  "videos",
 			Engines:   []string{"youtube"},
-			Metadata: map[string]any{
-				"channel":   item.Snippet.ChannelTitle,
-				"video_id": item.Snippet.ResourceID.VideoID,
-			},
 		})
 	}