arrstack: rebuild adult tier on the shared-Postgres pattern (#414)

## Why
Rebuild the ADULT arr tier on the same shared-Postgres, active-active pattern the kids tier now uses, replacing the legacy adult sonarr/radarr/nzbget. The old adult apps hold **no data**, so the wipe is sanctioned.

**Stacked on** `benvin/arrstack-kids` (#412) — review/merge that first.

## How
- **Add** `sonarr-adult` / `radarr-adult` / `nzbget-adult` (copies of the `*-kids` dirs, `s/kids/adult`):
  - own DBs `sonarr-adult-main` / `radarr-adult-main`, Vault paths `.../default/{sonarr,radarr}-adult(+-db)`
  - S3 prefixes `sonarr-adult` / `radarr-adult`; UrlBase + probe + exportarr URLs `/3aa168/{sonarr,radarr}` (adult hash)
  - media subPaths `tvshows/adult` + `movies/adult`; nzbget config PVC on `cephrbd-fast-delete`
- **postgres**: add managed roles `sonarr-adult`/`radarr-adult`, Database CRDs `{sonarr,radarr}-adult-main`, VaultStaticSecrets `{sonarr,radarr}-adult-db`
- **Remove** legacy `sonarr`/`radarr`/`nzbget` dirs (incl. their gateway/httproute), managed roles `sonarr`/`radarr`, databases `{sonarr,radarr}-main`, VSS `{sonarr,radarr}-db`, and all kustomization entries
- Third-party images stay canonical upstream; in-house images stay explicit `docker-internal`

`prowlarr`, `arrproxy`, and everything else untouched. arrproxy path re-wiring is a later PR.

Verified: `kustomize build` + `kubeconform` (87/87 valid), no dangling refs to removed apps, no `3df803` in adult files.
Reviewed-on: #414
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

apps/base/arrstack/kustomization.yaml

@@ -15,12 +15,12 @@ resources:
   - backups-bucket.yaml
   - postgres
   - valkey
-  - sonarr
-  - radarr
   - prowlarr
-  - nzbget
   - sonarr-kids
   - radarr-kids
   - nzbget-kids
+  - sonarr-adult
+  - radarr-adult
+  - nzbget-adult
   - arrproxy
   - mediamover