refactor(errs): migrate from gperr.Error to standard Go error interface

This is a large-scale refactoring across the codebase that replaces the custom
`gperr.Error` type with Go's standard `error` interface. The changes include:

- Replacing `gperr.Error` return types with `error` in function signatures
- Using `errors.New()` and `fmt.Errorf()` instead of `gperr.New()` and `gperr.Errorf()`
- Using `%w` format verb for error wrapping instead of `.With()` method
- Replacing `gperr.Subject()` calls with `gperr.PrependSubject()`
- Converting error logging from `gperr.Log*()` functions to zerolog's `.Err().Msg()` pattern
- Update NewLogger to handle multiline error message
- Updating `goutils` submodule to latest commit

This refactoring aligns with Go idioms and removes the dependency on
custom error handling abstractions in favor of standard library patterns.

internal/auth/userpass_test.go

@@ -27,7 +27,7 @@ func TestUserPassValidateCredentials(t *testing.T) {
 	err := auth.validatePassword("username", "password")
 	expect.NoError(t, err)
 	err = auth.validatePassword("username", "wrong-password")
-	expect.ErrorIs(t, ErrInvalidPassword, err)
+	expect.ErrorIs(t, bcrypt.ErrMismatchedHashAndPassword, err)
 	err = auth.validatePassword("wrong-username", "password")
 	expect.ErrorIs(t, ErrInvalidUsername, err)
 }