The AI module is preparing for the upcoming retirement of the Gemini embedding model currently in use. Existing AI embeddings created with deprecated models will be automatically refreshed in the background, helping keep AI features reliable without user action.

The model gemini-embedding-001 will be deprecated soon, so this commit is:
- Deprecating that model.
- Introducing an autovacuum to recompute embeddings that were done using embedding models that have been deprecated.

task-6004597