chore(router): Reorder postOriginHandlers to ensure custom modules …

[yokazawa]

@coderabbitai summary

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

This pull request updates the initialization logic for post-origin handlers in the Router to ensure custom modules' OnOriginResponse handlers are called before the HeaderPropagation handler. This change addresses an issue where HeaderPropagation was always executed first, preventing custom modules from processing the response.

Handler ordering fix:

• Changed initModules in router/core/router.go to collect custom modules' OnOriginResponse handlers separately and append them before existing handlers (such as HeaderPropagation), ensuring custom handlers are called first. [1] [2] [3]…execute before HeaderPropagation.