Fix Receiver type: gitea is not a valid Flux receiver type

The installed Flux version's Receiver CRD rejects type: gitea, which
failed dry-run validation and blocked the entire flux-system
Kustomization batch from applying - including the alaska/core stacks.
Switched to type: generic (no payload parsing needed for a trigger-only
webhook).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

clusters/production/webhook-receiver.yaml

@@ -6,9 +6,12 @@ metadata:
   name: gitea-receiver
   namespace: flux-system
 spec:
-  type: gitea
-  events:
-    - push
+  # This Flux version's Receiver CRD has no "gitea" type - valid values are
+  # generic, generic-hmac, generic-oidc, github, gitlab, bitbucket, harbor,
+  # dockerhub, quay, gcr, nexus, acr, cdevents. "generic" accepts any POST
+  # to the hook path without payload/signature parsing, which is fine here:
+  # worst case is an early sync trigger, not a permission escalation.
+  type: generic
   secretRef:
     name: gitea-webhook-token
   resources: