refactor: remove airtrail app manifests

Remove airtrail ArgoCD application registration and app manifests:
- manifests/_apps/airtrail.yaml (ArgoCD Application CR)
- manifests/airtrail/airtrail.yaml (Deployment, Service, Ingress, PVC)
- manifests/airtrail/pvs.yaml (PersistentVolumeClaim)

manifests/_apps/airtrail.yaml

@@ -1,25 +0,0 @@
-apiVersion: argoproj.io/v1alpha1
-kind: Application
-metadata:
-  name: airtrail
-  namespace: argocd
-  finalizers:
-  - resources-finalizer.argocd.argoproj.io
-spec:
-  project: cluster.fun
-  destination:
-    namespace: airtrail
-    name: cluster-fun (v2)
-  source:
-    path: manifests/airtrail
-    repoURL: "https://git.cluster.fun/AverageMarcus/cluster.fun.git"
-    targetRevision: HEAD
-  syncPolicy:
-    automated: {}
-    syncOptions:
-      - CreateNamespace=true
-  ignoreDifferences:
-  - kind: Secret
-    jsonPointers:
-    - /data
-