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/net/gphttp/loadbalancer/README.md

@@ -102,7 +102,7 @@ type LoadBalancer struct {
 func New(cfg *types.LoadBalancerConfig) *LoadBalancer
 
 // Start the load balancer as a background task
-func (lb *LoadBalancer) Start(parent task.Parent) gperr.Error
+func (lb *LoadBalancer) Start(parent task.Parent) error
 
 // Update configuration dynamically
 func (lb *LoadBalancer) UpdateConfigIfNeeded(cfg *types.LoadBalancerConfig)