Add jellyfin (HA fork) app under a new media project

Deploys the jellyfin-ha fork (git.unkin.net/unkin/jellyfin-ha) to au-syd1
via ArgoCD, under a dedicated media AppProject/ApplicationSet rather than
extending platform.

- New media AppProject + media-apps ApplicationSet (watches
  apps/overlays/*/jellyfin); registered in the argocd kustomizations
- apps/base/jellyfin: namespace, deployment (single replica to start),
  service, in-namespace Redis (transcode session store), gateway + httproute
  at jellyfin.k8s.syd1.au.unkin.net
- Storage: RWO config (cephrbd), RWX transcode scratch and RWX media
  library (cephfs) per the HA fork's pod-takeover requirement
- au-syd1 overlay

argocd/projects/kustomization.yaml

@@ -4,6 +4,7 @@ kind: Kustomization
 
 resources:
   - aitooling.yaml
+  - media.yaml
   - observability.yaml
   - platform.yaml
   - storage.yaml