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/watcher/file_watcher.go

@@ -2,16 +2,14 @@ package watcher
 
 import (
 	"context"
-
-	gperr "github.com/yusing/goutils/errs"
 )
 
 type fileWatcher struct {
 	relPath string
 	eventCh chan Event
-	errCh   chan gperr.Error
+	errCh   chan error
 }
 
-func (fw *fileWatcher) Events(ctx context.Context) (<-chan Event, <-chan gperr.Error) {
+func (fw *fileWatcher) Events(ctx context.Context) (<-chan Event, <-chan error) {
 	return fw.eventCh, fw.errCh
 }