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/acl/README.md

@@ -54,13 +54,13 @@ type Matchers []Matcher
 ### Exported functions and methods
 
 ```go
-func (c *Config) Validate() gperr.Error
+func (c *Config) Validate() error
 ```
 
 Validates configuration and sets defaults. Must be called before `Start`.
 
 ```go
-func (c *Config) Start(parent task.Parent) gperr.Error
+func (c *Config) Start(parent task.Parent) error
 ```
 
 Initializes the ACL, starts the logger and notification goroutines.
@@ -169,14 +169,14 @@ Configuration is loaded from `config/config.yml` under the `acl` key.
 
 ```yaml
 acl:
-  default: "allow"              # "allow" or "deny"
-  allow_local: true             # Allow private/loopback IPs
+  default: "allow" # "allow" or "deny"
+  allow_local: true # Allow private/loopback IPs
   log:
-    log_allowed: false          # Log allowed connections
+    log_allowed: false # Log allowed connections
   notify:
-    to: ["gotify"]              # Notification providers
-    interval: "1m"              # Notification interval
-    include_allowed: false      # Include allowed in notifications
+    to: ["gotify"] # Notification providers
+    interval: "1m" # Notification interval
+    include_allowed: false # Include allowed in notifications
 ```
 
 ### Hot-reloading

internal/acl/config.go

@@ -87,7 +87,7 @@ const (
 	ACLDeny  = "deny"
 )
 
-func (c *Config) Validate() gperr.Error {
+func (c *Config) Validate() error {
 	switch c.Default {
 	case "", ACLAllow:
 		c.defaultAllow = true
@@ -131,7 +131,7 @@ func (c *Config) Valid() bool {
 	return c != nil && c.valErr == nil
 }
 
-func (c *Config) Start(parent task.Parent) gperr.Error {
+func (c *Config) Start(parent task.Parent) error {
 	if c.Log != nil {
 		logger, err := accesslog.NewAccessLogger(parent, c.Log)
 		if err != nil {

internal/acl/matcher.go

@@ -2,6 +2,7 @@ package acl
 
 import (
 	"bytes"
+	"errors"
 	"net"
 	"strings"
 
@@ -38,9 +39,9 @@ var errMatcherFormat = gperr.Multiline().AddLines(
 )
 
 var (
-	errSyntax      = gperr.New("syntax error")
-	errInvalidIP   = gperr.New("invalid IP")
-	errInvalidCIDR = gperr.New("invalid CIDR")
+	errSyntax      = errors.New("syntax error")
+	errInvalidIP   = errors.New("invalid IP")
+	errInvalidCIDR = errors.New("invalid CIDR")
 )
 
 func (matcher *Matcher) Parse(s string) error {