## Why
The cluster runs the arrstack forks at `-unkin3`. Ben merged two workstreams into each fork's `main`:
- **Redis SignalR backplane + cross-replica cache invalidation** — SignalR messages and cache-invalidation events fan out across replicas via Redis, so any replica serves consistent live UI/state.
- **MediaCover -> S3 + backups -> S3** — MediaCover (sonarr/radarr) and backups (all three) use an optional S3 store, so any stateless replica can serve covers and write/restore backups.
Fresh `-unkin4` tags were cut on each fork's `main` HEAD, building `docker-internal/<app>:<base>-unkin4` images. This bumps the deployment images so ArgoCD rolls the merged work into the cluster.
## Changes
- Bump sonarr app image `v5.0.0-unkin3` -> `v5.0.0-unkin4`
- Bump radarr app image `v6.4.2-unkin3` -> `v6.4.2-unkin4`
- Bump prowlarr app image `v2.6.2-unkin3` -> `v2.6.2-unkin4`
The waitfordb initContainer and bucket resources are unchanged; only the app-container `image:` tags move.
Reviewed-on: #390
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>
unkin-agent
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