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

template-chart/values.yaml

@@ -1,7 +1,16 @@
+# Scale the whole chart down without uninstalling it: scaleDown: true renders
+# every Deployment/StatefulSet with replicas: 0 (and suspends CronJobs) and
+# takes precedence over any per-workload replicas value. PVCs, Secrets and
+# Services stay in place; scaleDown: false brings the workloads back up.
+scaleDown: false
+
 secrets:
   xxxSecretRef: null
 
 xxx:
+  # Replica count for this workload; 0 is allowed and scales it down.
+  # The chart-global scaleDown flag takes precedence.
+  replicas: 1
   resources:
     # Limits are optional: memory and ephemeral-storage limits default to
     # limitFactor x the request, an explicitly set limit always wins, and a
@@ -74,4 +83,4 @@ storage:
 ingress:
   enabled: true
   clusterIssuer: null
-  domain: null
+  domain: null