feat(cyberchef)!: NetworkPolicy, on by default

Major, as every chart in this rollout is: networkPolicy.enabled defaults to
true, so the object reaches running releases on the next upgrade.

The simplest policy of the sweep, and the one to read first. CyberChef is a
static web app - nginx serves files, the recipes run in the visitor's browser,
the pod holds no state and calls nothing - so what the policy buys is the two
CEILINGS rather than any source restriction: inbound is capped at 8080, the
single port the pod declares, and outbound at DNS, which is as tight as the
object goes without breaking name resolution.

The 8080 rule carries no source selector by default, and that is deliberate
rather than an oversight: 8080 is the port all three probes address, and the
kubelet probes from the IP of the worker node running the pod, which no chart
can know. Guessing it wrong leaves the pod permanently un-Ready, a symptom that
reads as a broken application. Narrowing it is networkPolicy.probeSources, and
the restricted branch then also carries the ingress controller - measured as
the rke2-traefik DaemonSet in kube-system, which serves this chart's HTTPRoute
as well, since the same Traefik backs the Gateway API here.

Part of #5

cyberchef/templates/NOTES.txt

@@ -108,3 +108,49 @@ cyberchef.env HAS NO EFFECT ON THE APP
   files, but the served CyberChef bundle is static and reads none of them —
   configuration has to happen in the browser.
 {{- end }}
+{{- if .Values.networkPolicy.enabled }}
+
+NETWORKPOLICY IS ACTIVE — WHAT IT CAPS, AND WHAT IT DOES NOT
+  {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy selects this workload's pods.
+  Inbound: TCP 8080 only, the single port this pod declares. Outbound: DNS{{ with .Values.networkPolicy.egress }}{{ with .extraPorts }}
+  plus TCP {{ join ", " . }}{{ end }}{{ end }} — a static file server needs nothing more.
+
+  Three limits belong in the same breath, because none of them is visible in
+  the object itself:
+
+  - EGRESS IS BY PORT, NEVER BY DESTINATION. A NetworkPolicy matches CIDRs and
+    selectors and cannot express a hostname, so every egress rule permits its
+    port to ANY address. That is a limit of the object, not a shortcut — this
+    cluster's CNI (Canal: Flannel plus Calico) has no FQDN rule either. An
+    outbound port the chart does not know about is BLOCKED: add it to
+    networkPolicy.egress.extraPorts, and expect to find out through an
+    application-level connection error rather than through this object.
+{{- if .Values.networkPolicy.probeSources }}
+  - THE PROBE PATH IS RESTRICTED in this release, because
+    networkPolicy.probeSources is set to
+      {{ join ", " .Values.networkPolicy.probeSources }}
+    Probes come from the IP of the WORKER NODE running the pod. If none of those
+    CIDRs covers the node this pod lands on, the kubelet's probes are dropped
+    and THE POD NEVER BECOMES READY — the rollout then times out and the symptom
+    looks like a broken application. Compare
+
+      kubectl -n {{ .Release.Namespace }} describe pod -l app={{ .Release.Name }}-{{ .Chart.Name }}-deployment
+
+    against `kubectl get node -o wide`.
+{{- else }}
+  - THE PROBED PORT IS OPEN INSIDE THE CLUSTER. networkPolicy.probeSources is
+    empty, so that rule carries no source selector at all and any pod the CNI
+    routes to can reach it. Not from the internet — but this is NOT pod-level
+    isolation. Narrowing it means listing the worker node IPs in
+    networkPolicy.probeSources, because the kubelet probes from the node's own
+    address and the chart cannot know it; a wrong guess there leaves the pod
+    permanently un-Ready.
+{{- end }}
+  - IT IS ONLY A BOUNDARY WHERE THE CNI ENFORCES POLICIES. Where it does not,
+    this object is accepted and filters nothing, so everything reads as
+    configured while nothing is filtered. `kubectl -n {{ .Release.Namespace }} get networkpolicy`
+    shows the object exists; only a connection attempt from an unrelated
+    namespace shows that it bites.
+
+  Switch it off with networkPolicy.enabled: false.
+{{- end }}