Rename smartrun to geniusrun throughout the codebase

Updates the Go module path, cmd/smartrund -> cmd/geniusrund, the
smartrun-dev skill, .gitignore, and every reference in docs/CLAUDE.md
to match.

backend/internal/api/activities.go

@@ -6,7 +6,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
-	"smartrun/backend/internal/store"
+	"geniusrun/backend/internal/store"
 )
 
 // activityListItem is one row of the activities list, enriched with its