ci: align workflows with pipeline-actions; move haven-notify spec to haven

- haven-notify.yaml: replace hand-rolled build+deploy (broken
  docker/build-push-action remote-builder path) with pipeline-actions
  build-and-push + deploy-restart composite actions; full Gitea uses:
  URLs; ubuntu-amd64 runner label.
- main.yaml / test-automated-nfs-backup.yaml: fix runner label
  ubuntu-latest -> ubuntu-amd64.
- Remove haven-notify/deploy manifest; it now lives in the haven
  homelab repo at infra/haven-notify.yaml. Update README accordingly.

haven-notify/deploy/haven-notify.yaml

@@ -1,71 +0,0 @@
-apiVersion: apps/v1
-kind: Deployment
-metadata:
-  name: haven-notify
-  labels:
-    app: haven-notify
-spec:
-  replicas: 1
-  selector:
-    matchLabels:
-      app: haven-notify
-  template:
-    metadata:
-      labels:
-        app: haven-notify
-    spec:
-      containers:
-        - name: haven-notify
-          image: git.ivanch.me/ivanch/haven-notify:latest
-          imagePullPolicy: Always
-          ports:
-            - containerPort: 8080
-          env:
-          - name: WEBHOOK_URL
-            valueFrom:
-              secretKeyRef:
-                name: discord-webhook
-                key: HAVEN_WEBHOOK_URL
-          readinessProbe:
-            httpGet:
-              path: /ready
-              port: 8080
-            initialDelaySeconds: 5
-            periodSeconds: 10
-          livenessProbe:
-            httpGet:
-              path: /live
-              port: 8080
-            initialDelaySeconds: 5
-            periodSeconds: 10
----
-apiVersion: v1
-kind: Service
-metadata:
-  name: haven-notify
-spec:
-  selector:
-    app: haven-notify
-  ports:
-    - protocol: TCP
-      port: 8080
-      targetPort: 8080
----
-apiVersion: networking.k8s.io/v1
-kind: Ingress
-metadata:
-  name: haven-notify
-  namespace: default
-spec:
-  ingressClassName: nginx
-  rules:
-    - host: notify.haven
-      http:
-        paths:
-          - path: /
-            pathType: Prefix
-            backend:
-              service:
-                name: haven-notify
-                port:
-                  number: 8080