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/garmin/mock/mock.go

@@ -5,7 +5,7 @@ package mock
 import (
 	"context"
 
-	"smartrun/backend/internal/garmin"
+	"geniusrun/backend/internal/garmin"
 )
 
 // Client is a fake garmin.Client returning data supplied by the test/caller.