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>

apps/base/reposync/configmap_openvox-repo.yaml

@@ -0,0 +1,17 @@
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  labels:
+    app.kubernetes.io/component: reposync-openvox7
+    app.kubernetes.io/name: reposync
+  name: openvox7-openvox-repo
+  namespace: reposync
+data:
+  openvox.repo: |
+    [openvox]
+    name=openvox repository
+    baseurl=https://artifactapi.k8s.syd1.au.unkin.net/api/v1/remote/openvox/openvox7/el/9/x86_64/
+    gpgkey=https://artifactapi.k8s.syd1.au.unkin.net/api/v1/remote/openvox/GPG-KEY-openvox.pub
+    enabled=1
+    gpgcheck=1