* chore: do not mount lightpush without relay (fixes#2808)
- Change mountLightPush signature to return Result[void, string]
- Return error when relay is not mounted
- Update all call sites to handle Result return type
- Add test verifying mounting fails without relay
- Only advertise lightpush capability when relay is enabled
* chore: don't mount legacy lightpush without relay
* Rename waku_api to rest_api and underlying rest to endpoint for clearity
* Rename node/api to node/kernel_api to suggest that it is an internal accessor to node interface + make everything compile after renaming
* make waku api a top level import
* fix use of relative path imports and use default to root rather in case of waku and tools modules
