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/profile.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 	"net/http"
 
-	"smartrun/backend/internal/store"
+	"geniusrun/backend/internal/store"
 )
 
 // validateProfile checks the HR zones are ascending and gap-free once they