Add per-workload replicas values and a chart-global scaleDown flag

Every Deployment/StatefulSet now takes its replica count from a replicas
value (default 1, explicit 0 allowed) via a new per-chart <chart>.replicas
helper; the helper uses a kindIs "invalid" nil check so an explicit 0 is
not swallowed by Helm's default function. A chart-global scaleDown flag
(default false) takes precedence: it renders every workload with
replicas: 0 and suspends the paperless-ngx consume CronJob, stopping the
app without uninstalling it (PVCs, Secrets, Services and Ingress remain).

Defaults leave the rendered manifests byte-identical to main, so all
published charts get a minor version bump; the template-chart carries the
reference helper implementation and stays unversioned.

Fixes #25

patchmon/templates/patchmon-frontend.deployment.yaml

@@ -5,7 +5,7 @@ metadata:
   labels:
     app: {{ .Release.Name }}-{{ .Chart.Name }}-frontend
 spec:
-  replicas: 1
+  replicas: {{ include "patchmon.replicas" (dict "scaleDown" .Values.scaleDown "replicas" .Values.patchmon.frontend.replicas) }}
   selector:
     matchLabels:
       app: {{ .Release.Name }}-{{ .Chart.Name }}-frontend