fix: warning error for slog

[diofeher]

When running tests:

cmd/run-server/main.go:21:41: slog.Logger.Error arg "err" should be a string or a slog.Attr (possible missing key or value)
cmd/run-server/main.go:32:42: slog.Logger.Error arg "err" should be a string or a slog.Attr (possible missing key or value)

Fixed this.

[cam72cam]

Thanks @diofeher !