Allow external integrations to declare their own scene triggers/actions

Hi everyone :waving_hand:

Development is ready, and I would need a few testers to check that it meets the requirements before going into production :grinning_face_with_smiling_eyes:

Here is the result:

The PR containing the spec is here:

You can test with this Docker image:

ghcr.io/gladysassistant/gladys-preview:claude-wonderful-albattani-8v9pbw

All feedback is welcome! If everything is good, I plan to publish this on Monday :rocket: