fix(swagger): guard against undefined module routes in SwaggerScanner

[hibo-developer]

Hello maintainers,

I found a runtime TypeError in SwaggerScanner where it calls .values() on an undefined routes when deep scanning related modules. This causes startup failures in apps that have modules without controller routes.

I prepared a fix that:

• Skips related modules without routes when deep scanning
• Guards scanModuleRoutes to return [] if routes is undefined

A full patch and tests are available in my repo here: https://github.com/hibo-developer/hibo_cocina/pull/1

Patch file (suggested):

(see attached patch in backend/patches/@nestjs+swagger+6.3.0.patch)

Please let me know if you'd like a PR with the change applied directly to the codebase; I can fork and open a PR (currently attempted, waiting on fork readiness). Thanks!

[kamilmysliwiec]

Please provide a minimum reproduction repository (Git repository/StackBlitz/CodeSandbox project).