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/server.go

@@ -1,4 +1,4 @@
-// Package api is smartrun's HTTP layer: REST handlers over internal/store,
+// Package api is geniusrun's HTTP layer: REST handlers over internal/store,
 // internal/garmin, and internal/sync.
 package api
 
@@ -11,9 +11,9 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
-	"smartrun/backend/internal/garmin"
-	"smartrun/backend/internal/store"
-	appsync "smartrun/backend/internal/sync"
+	"geniusrun/backend/internal/garmin"
+	"geniusrun/backend/internal/store"
+	appsync "geniusrun/backend/internal/sync"
 )
 
 // Server wires the HTTP handlers to the app's dependencies.