feat: remove ArgoCD Image Updater, replaced by Forgejo webhook

Image promotion now handled by api-gw webhook endpoint
(/v1/webhooks/forgejo) which patches ArgoCD Application CRs
on Forgejo package push events (homelab-frontend PR #55).

- Delete Image Updater Application and values
- Remove argocd-image-updater.argoproj.io annotations from all apps
- Registry secrets kept (used by webhook digest queries + imagePullSecrets)

k8s/infra/argocd-image-updater/values.yaml

@@ -1,70 +0,0 @@
-# ArgoCD Image Updater configuration
-# Watches Forgejo registry and updates ArgoCD Applications with new image tags
-
-config:
-  # Registry configuration - Forgejo allows anonymous pulls
-  registries:
-    - name: forgejo
-      api_url: https://forgejo.riotpiao.com
-      prefix: forgejo.riotpiao.com
-      default: true
-      insecure: false
-
-  # Log level
-  logLevel: debug
-
-  # ArgoCD API server
-  argocd:
-    grpcWeb: true
-    serverAddress: argocd-server.argocd.svc.cluster.local
-    insecure: true
-    plaintext: true
-
-  # Git write-back configuration (for multi-source Applications)
-  git:
-    # Commit author for image updates
-    user:
-      name: "ArgoCD Image Updater"
-      email: "[email protected]"
-    # Use SSH keys from ArgoCD's known hosts + credentials
-    # Image Updater inherits ArgoCD's git credentials (mounted via ArgoCD secret)
-
-# Mount ArgoCD's git credentials for write-back
-extraVolumes:
-  - name: argocd-ssh-known-hosts-cm
-    configMap:
-      name: argocd-ssh-known-hosts-cm
-      defaultMode: 0644
-  - name: argocd-gpg-keys-cm
-    configMap:
-      name: argocd-gpg-keys-cm
-      optional: true
-      defaultMode: 0644
-  - name: argocd-gpg-pubring
-    configMap:
-      name: argocd-gpg-pubring-cm
-      optional: true
-      defaultMode: 0644
-
-extraVolumeMounts:
-  - name: argocd-ssh-known-hosts-cm
-    mountPath: /etc/ssh/ssh_known_hosts.d/argocd-ssh-known-hosts
-    subPath: ssh_known_hosts
-  - name: argocd-gpg-keys-cm
-    mountPath: /etc/gpg/source
-  - name: argocd-gpg-pubring
-    mountPath: /etc/gpg/pubring
-
-# Extra environment variables
-extraEnv:
-  - name: GIT_SSH_KNOWN_HOSTS_CONFIG_MAP_ENABLED
-    value: "true"
-
-# Resources
-resources:
-  requests:
-    cpu: 50m
-    memory: 64Mi
-  limits:
-    cpu: 200m
-    memory: 128Mi