feat: move housekeeper to cronjob or make redundant deployment possible

Ideally the housekeeper could run as cronjob.

Currently the housekeeper runs as single instance, and syncs a lot of state from database to Redis. It also keeps some state around to not perform the expensive operations multiple times if not necessary.

The expensive operations are mostly
1. writing all validators from the beacon node to redis
2. writing all validator registrations from the database to redis

These are currently a redis command per entry, but could possibly be made batch requests.

Start by locating the housekeeper entry point and the code that syncs beacon-node validators and database registrations into Redis. Compare the current single-instance assumptions with the cronjob or redundant-deployment options, including whether batch Redis requests preserve the existing state tracking. Done means one clearly chosen operating model is implemented and the expensive sync work remains correct.

Written by the indexing model from the issue text.