feat(cloudflare-ddns): keep aleshym.co pointed at the current WAN IP

The WAN is on DHCP with no DDNS anywhere, so a lease change would break
public DNS silently -- certs, Plex and Gitea SSH all resolve through
aleshym.co. cert-manager's Cloudflare token only ever writes the
_acme-challenge TXT records and never touches the A record.

Reuses that same token, resealed for this namespace: its Zone:DNS:Edit
scope already covers A records (verified against the live API).

The updater only PATCHes when the record is actually stale, and PATCHes
content alone so the proxied flag and TTL stay as configured. It exits
non-zero on any failure so a broken run surfaces as a Failed job rather
than dying quietly -- silent failure is the thing this exists to prevent.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

argocd/cloudflare-ddns.yaml

@@ -0,0 +1,20 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: cloudflare-ddns
+  namespace: argocd
+spec:
+  project: default
+  source:
+    repoURL: https://git.aleshym.co/funman300/k3s-homelab.git
+    targetRevision: main
+    path: apps/cloudflare-ddns
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: cloudflare-ddns
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+      - CreateNamespace=true