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/projects/platform.yaml

@@ -35,6 +35,8 @@ spec:
       server: https://kubernetes.default.svc
     - namespace: 'woodpecker'
       server: https://kubernetes.default.svc
+    - namespace: 'reposync'
+      server: https://kubernetes.default.svc
   clusterResourceWhitelist:
     - group: ''
       kind: Namespace