feat: migrate reposync to ArgoCD

Migrate repository sync cronjobs from Terragrunt to ArgoCD/Kustomize.
Adds four daily CronJobs (almalinux9-baseos, almalinux9-appstream, epel9,
openvox7) with associated PVCs and ConfigMaps in the reposync namespace.

💘 Generated with Crush

Assisted-by: Claude Sonnet 4.6 via Crush <crush@charm.land>

argocd/applicationsets/platform.yaml

@@ -23,6 +23,7 @@ spec:
       - path: apps/overlays/*/jfrog
       - path: apps/overlays/*/puppet
       - path: apps/overlays/*/woodpecker
+      - path: apps/overlays/*/reposync
   template:
     metadata:
       name: 'platform-{{path[3]}}'  # cluster-app format (e.g., platform-reflector-system)