chore: update golangci-lint to v2.13.0

Migrate the deprecated gofumpt `extra-rules` to `extra.group-params`, as
the alias now also enables the new `clothe-returns` and `balance-calls`
rules. Disable SA4023, which hangs on go 1.27, see
https://github.com/golangci/golangci-lint/issues/6732.

Apply the resulting modernize fixes, mostly flattening embedded struct
literals and switching errors.As to errors.AsType.

Assisted-by: Claude:Opus 5

services/auth/source/db/assert_interface_test.go

@@ -17,4 +17,4 @@ type sourceInterface interface {
 	auth_model.Config
 }
 
-var _ (sourceInterface) = &db.Source{}
+var _ sourceInterface = &db.Source{}