feat(08-01): add ServiceMonitor for Prometheus scraping

- Create ServiceMonitor template for Prometheus Operator discovery
- Add metrics.enabled and metrics.interval to values.yaml
- ServiceMonitor selects TaskPlanner pods via selectorLabels
- Scrapes /metrics endpoint every 30s by default

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

helm/taskplaner/templates/servicemonitor.yaml

@@ -0,0 +1,19 @@
+{{- if .Values.metrics.enabled }}
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: {{ include "taskplaner.fullname" . }}
+  labels:
+    {{- include "taskplaner.labels" . | nindent 4 }}
+spec:
+  selector:
+    matchLabels:
+      {{- include "taskplaner.selectorLabels" . | nindent 6 }}
+  endpoints:
+    - port: http
+      path: /metrics
+      interval: {{ .Values.metrics.interval | default "30s" }}
+  namespaceSelector:
+    matchNames:
+      - {{ .Release.Namespace }}
+{{- end }}

helm/taskplaner/values.yaml

@@ -111,6 +111,11 @@ basicAuth:
   # Example: "admin:$apr1$xyz..."
   htpasswd: ""
 
+# Prometheus metrics
+metrics:
+  enabled: true
+  interval: 30s
+
 # Application-specific configuration
 config:
   # The external URL where the app is accessible (required for CSRF protection)