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/forgejo/forgejo-server/values.yaml

@@ -174,10 +174,9 @@ service:
 
 image:
   pullPolicy: "IfNotPresent"
-  # Overrides the image tag whose default is the chart appVersion.
-  #tag: "8.0.3"
-  # Adds -rootless suffix to image name
-  # rootless: true
-  fullOverride: edp.buildth.ing/devfw-cicd/edp-forgejo:14.0.2-edp1-rootless
+  # DB has v15a/v15b migrations from workflow-webhook build.
+  # Using that image until a proper v15+ EDP release is cut.
+  # DO NOT revert — automated upload will break the DB schema.
+  fullOverride: edp.buildth.ing/devfw-cicd/edp-forgejo:workflow-webhook-20260305
 
 forgejo: {}