feat: AlertManager Matrix integration with severity routing

Deploy matrix-alertmanager-receiver bridge (pending bot credentials in
OpenBao). Update AlertManager routing: critical → Matrix + email,
warning → Matrix only, Watchdog → null. Reduce repeat interval to 4h.

base/monitoring/matrix-alertmanager-receiver-deployment.yaml

@@ -0,0 +1,65 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: matrix-alertmanager-receiver
+  namespace: monitoring
+  labels:
+    app: matrix-alertmanager-receiver
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: matrix-alertmanager-receiver
+  template:
+    metadata:
+      labels:
+        app: matrix-alertmanager-receiver
+    spec:
+      containers:
+        - name: receiver
+          image: ghcr.io/metio/matrix-alertmanager-receiver:2024.11.27
+          ports:
+            - containerPort: 3000
+              protocol: TCP
+          env:
+            - name: MAR_HOMESERVER_URL
+              value: "http://tuwunel.matrix.svc.cluster.local:6167"
+            - name: MAR_USER_ID
+              value: "@alertbot:sunbeam.pt"
+            - name: MAR_ACCESS_TOKEN
+              valueFrom:
+                secretKeyRef:
+                  name: matrix-bot-creds
+                  key: access_token
+            - name: MAR_ROOM_MAPPING
+              value: "ops=$(ROOM_ID)"
+            - name: ROOM_ID
+              valueFrom:
+                secretKeyRef:
+                  name: matrix-bot-creds
+                  key: room_id
+            - name: MAR_PORT
+              value: "3000"
+          resources:
+            requests:
+              cpu: 10m
+              memory: 32Mi
+            limits:
+              memory: 64Mi
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: matrix-alertmanager-receiver
+  namespace: monitoring
+  labels:
+    app: matrix-alertmanager-receiver
+spec:
+  type: ClusterIP
+  ports:
+    - port: 3000
+      targetPort: 3000
+      protocol: TCP
+  selector:
+    app: matrix-alertmanager-receiver

base/monitoring/matrix-bot-secret.yaml

@@ -0,0 +1,27 @@
+---
+# Matrix alertbot credentials from OpenBao KV at secret/alertbot.
+apiVersion: secrets.hashicorp.com/v1beta1
+kind: VaultStaticSecret
+metadata:
+  name: matrix-bot-creds
+  namespace: monitoring
+spec:
+  vaultAuthRef: vso-auth
+  mount: secret
+  type: kv-v2
+  path: alertbot
+  refreshAfter: 30s
+  rolloutRestartTargets:
+    - kind: Deployment
+      name: matrix-alertmanager-receiver
+  destination:
+    name: matrix-bot-creds
+    create: true
+    overwrite: true
+    transformation:
+      excludeRaw: true
+      templates:
+        access_token:
+          text: "{{ index .Secrets \"access_token\" }}"
+        room_id:
+          text: "{{ index .Secrets \"room_id\" }}"

base/monitoring/prometheus-values.yaml

@@ -138,13 +138,35 @@ alertmanager:
       group_by: [alertname, namespace]
       group_wait: 30s
       group_interval: 5m
-      repeat_interval: 12h
-      receiver: email
+      repeat_interval: 4h
+      receiver: matrix
+      routes:
+        - matchers:
+            - alertname = Watchdog
+          receiver: "null"
+        - matchers:
+            - severity = critical
+          receiver: critical
+        - matchers:
+            - severity = warning
+          receiver: matrix
     receivers:
+      - name: "null"
       - name: email
         email_configs:
           - to: "ops@DOMAIN_SUFFIX"
             send_resolved: true
+      - name: matrix
+        webhook_configs:
+          - url: "http://matrix-alertmanager-receiver.monitoring.svc.cluster.local:3000/alerts"
+            send_resolved: true
+      - name: critical
+        webhook_configs:
+          - url: "http://matrix-alertmanager-receiver.monitoring.svc.cluster.local:3000/alerts"
+            send_resolved: true
+        email_configs:
+          - to: "ops@DOMAIN_SUFFIX"
+            send_resolved: true
 
 # Disable monitors for components k3s doesn't expose
 kubeEtcd: