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/utils.go

@@ -1,20 +1,20 @@
 package auth
 
 import (
+	"errors"
 	"net"
 	"net/http"
 	"strings"
 	"time"
 
 	"github.com/yusing/godoxy/internal/common"
-	gperr "github.com/yusing/goutils/errs"
 	strutils "github.com/yusing/goutils/strings"
 )
 
 var (
-	ErrMissingSessionToken = gperr.New("missing session token")
-	ErrInvalidSessionToken = gperr.New("invalid session token")
-	ErrUserNotAllowed      = gperr.New("user not allowed")
+	ErrMissingSessionToken = errors.New("missing session token")
+	ErrInvalidSessionToken = errors.New("invalid session token")
+	ErrUserNotAllowed      = errors.New("user not allowed")
 )
 
 func IsFrontend(r *http.Request) bool {