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/README.md

@@ -93,8 +93,8 @@ const (
 
 ```go
 // Validation and lifecycle
-func (r *Route) Validate() gperr.Error
-func (r *Route) Start(parent task.Parent) gperr.Error
+func (r *Route) Validate() error
+func (r *Route) Start(parent task.Parent) error
 func (r *Route) Finish(reason any)
 func (r *Route) Started() <-chan struct{}
 
@@ -119,8 +119,8 @@ func (r *Route) UseHealthCheck() bool
 ```mermaid
 classDiagram
     class Route {
-        +Validate() gperr.Error
-        +Start(parent) gperr.Error
+        +Validate() error
+        +Start(parent) error
         +Finish(reason)
         +Started() &lt;-chan struct#123;#125;
     }