fix(dev): 🐛 revert automated-upload damage — restore working image pins + OIDC secrets

Automated upload (95deeef) overwrote 5 manually-pinned values:

- forgejo-server: restore workflow-webhook-20260305 (DB has v15a/v15b
  migrations; rolling back to 14.0.2-edp1-rootless WILL break the DB)
- garm: restore v0.1.7-forgejo-22 (v0.1.7-forgejo-23 has exec format
  error — wrong arch build, crashes on OTC CCE amd64 nodes)
- sizer-receiver/secret.yaml: re-add sizer-oidc-client secret (deleted
  by upload; causes OIDC auth failure on every sizer-receiver login)
- dex/manifests/dex-sizer-client.yaml: re-add (deleted by upload;
  dex cannot resolve sizer OIDC client without this secret)
- dex.yaml: restore manifests source block (removed by upload;
  without it ArgoCD never deploys the dex/manifests/ directory)

backup-alerts.yaml (new VMRule from automated upload) is kept as-is.

otc/dev.t09.de/stacks/garm/garm/values.yaml

@@ -26,7 +26,10 @@ credentials:
 
 image:
   repository: edp.buildth.ing/devfw-cicd/garm-forgejo
-  tag: v0.1.7-forgejo-23
+  # NOTE: v0.1.7-forgejo-23 has exec format error (wrong arch build).
+  # Rolled back to -22 until -23 is rebuilt for amd64.
+  # DO NOT bump — automated upload will restore wrong arch.
+  tag: v0.1.7-forgejo-22
 
 providerConfig:
   edgeConnect: