feat: Wikidata engine and Wikipedia knowledge infobox

- Add wikidata engine (wbsearchentities), tests, factory/planner/config
- Wikipedia REST summary: infobox from extract, thumbnail, article URL
- InfoboxView URL; render infobox list in results_inner + base styles
- Preferences Wikidata toggle; engine badge color for wikidata

Made-with: Cursor

internal/views/views.go

@@ -96,6 +96,7 @@ type InfoboxView struct {
 	Title   string
 	Content string
 	ImgSrc  string
+	URL     string
 }
 
 // FilterOption represents a filter radio option for the sidebar.
@@ -273,7 +274,10 @@ func FromResponse(resp contracts.SearchResponse, query string, pageno int, activ
 		if v, ok := ib["img_src"].(string); ok {
 			iv.ImgSrc = util.SanitizeResultURL(v)
 		}
-		if iv.Title != "" || iv.Content != "" {
+		if v, ok := ib["url"].(string); ok {
+			iv.URL = util.SanitizeResultURL(v)
+		}
+		if iv.Title != "" || iv.Content != "" || iv.ImgSrc != "" {
 			pd.Infoboxes = append(pd.Infoboxes, iv)
 		}
 	}