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/route/provider/event_handler.go

@@ -81,7 +81,7 @@ func (handler *EventHandler) match(event watcher.Event, route *route.Route) bool
 func (handler *EventHandler) Add(parent task.Parent, route *route.Route) {
 	err := handler.provider.startRoute(parent, route)
 	if err != nil {
-		handler.errs.Add(err.Subject("add"))
+		handler.errs.AddSubjectf(err, "add")
 	}
 }
 
@@ -93,7 +93,7 @@ func (handler *EventHandler) Update(parent task.Parent, oldRoute *route.Route, n
 	oldRoute.FinishAndWait("route update")
 	err := handler.provider.startRoute(parent, newRoute)
 	if err != nil {
-		handler.errs.Add(err.Subject("update"))
+		handler.errs.AddSubjectf(err, "update")
 	}
 }