fix: staticcheck and go mod tidy

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

cmd/lazysecrets/share.go

@@ -26,7 +26,7 @@ func shareFiles(ctx context.Context, providers []provider.Provider, st *store.St
 		return err
 	}
 	if fs.NArg() == 0 {
-		return errors.New("usage: lazysecrets share [--key <link>] <env file>...")
+		return errors.New("usage: lazysecrets share [--key <link>] <env files>")
 	}
 
 	var root, id string