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/rules/help.go

@@ -131,7 +131,7 @@ Generate help string as error, e.g.
 		from: the path to rewrite, must start with /
 		to: the path to rewrite to, must start with /
 */
-func (h *Help) Error() gperr.Error {
+func (h *Help) Error() error {
 	var lines gperr.MultilineError
 
 	lines.Adds(ansi.WithANSI(h.command, ansi.HighlightGreen))