add: actual-budget-exporter app

Prometheus exporter for Actual Budget. actual_server itself stays in
homelab-docker-compose-prod (host docker-compose), exporter only scrapes it
over LAN and exposes /metrics via a ServiceMonitor. No HTTPRoute. Password
and budget ID come from a hand-created Secret, not committed.

apps/actual-budget-exporter/chart/templates/service.yaml

@@ -0,0 +1,14 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: {{ .Release.Name }}
+  labels:
+    app: {{ .Release.Name }}
+spec:
+  type: {{ .Values.service.type }}
+  selector:
+    app: {{ .Release.Name }}
+  ports:
+    - name: metrics
+      port: {{ .Values.service.port }}
+      targetPort: {{ .Values.service.port }}