feat(outline)!: NetworkPolicy, on by default

Major, as every chart in this rollout is.

Inbound 3000 only; outbound DNS plus 5432, 6379 and 443. Those three egress
ports are the STANDARD ones and not the configured ones, which is this chart's
real limitation and is written into values.yaml, the template header and
NOTES.txt rather than left to be discovered: Outline's database, Redis and OIDC
provider all arrive as connection URLs inside 1Password items that the chart
never parses, so it cannot know where they listen and cannot validate a guess.
A dependency on another port is blocked, and because all three probes hit
/_health - which checks Postgres and Redis - the symptom is a pod that never
becomes Ready rather than an error anyone reads. networkPolicy.egress.extraPorts
is the escape hatch.

That same property is what makes this chart the right place for the enforcement
experiment in the next commit.

Also reverts the cyberchef fixture from the first experiment: with the probe
port restricted to an address that is not the node's, the install-test went
GREEN, so the claim that it catches a blocked probe path does not hold as
written. The next commit establishes whether policies are enforced in CI at
all.

Part of #5

outline/values.schema.json

@@ -9,6 +9,57 @@
       "description": "Helm's conventional cross-chart values. Unused by this chart, kept open so an umbrella install cannot break on it.",
       "type": "object"
     },
+    "networkPolicy": {
+      "description": "The chart's NetworkPolicy (Gitea #5), on by default. A ceiling on reachability and not an authentication layer: only the declared container ports are reachable at all, egress is capped by PORT (a NetworkPolicy matches CIDRs and selectors, never hostnames, so a destination host cannot be expressed), and ingress is capped by source for every port no network probe touches. Only a boundary where the cluster's CNI enforces policies - an unenforced policy is accepted by the API server and filters nothing. The template's header carries the full list of what it does not do.",
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "enabled": {
+          "type": "boolean"
+        },
+        "allowedNamespaces": {
+          "description": "Namespaces whose pods may reach this workload, in addition to the release's own namespace, which is always allowed. Matched on the kubernetes.io/metadata.name label Kubernetes sets on every namespace itself, so no labelling work is needed - and no typo protection either: a name that does not exist matches nothing and is silently ineffective. An entry opens the port to EVERY pod in that namespace; for the ingress controller use ingressController instead.",
+          "type": ["array", "null"],
+          "items": {
+            "type": "string"
+          }
+        },
+        "probeSources": {
+          "description": "Source CIDRs allowed to reach the port the network probes address. EMPTY MEANS OPEN, not blocked: with no entry that rule is rendered without a \"from\" selector. The kubelet's probes come from the IP of the worker node running the pod, an address the chart cannot know and must not guess - a guessed CIDR that excludes the real node blocks every probe and the pod never becomes Ready, which reads as a broken application rather than as a policy. Setting this restricts the rule, which is why the chart adds the own namespace, ingressController and allowedNamespaces to the same rule.",
+          "type": ["array", "null"],
+          "items": {
+            "type": "string"
+          }
+        },
+        "ingressController": {
+          "description": "The ingress controller allowed to reach the routed port once probeSources restricts it; rendered only while ingress.enabled or httpRoute.enabled is true. The two keys become ONE \"from\" entry and are therefore an AND - pods carrying podLabels IN namespace - which is the whole point: the controller's namespace in allowedNamespaces would open the port to every pod in kube-system. The default is measured on this cluster (DaemonSet rke2-traefik in kube-system, which also serves the Gateway API here), not assumed; a policy written against the wrong controller is accepted, looks strict and silently blocks all web traffic.",
+          "type": ["object", "null"],
+          "additionalProperties": false,
+          "properties": {
+            "namespace": {
+              "type": ["string", "null"]
+            },
+            "podLabels": {
+              "description": "Label set the controller's pods carry, rendered verbatim as a podSelector's matchLabels. Kept open because the chart does not interpret the keys.",
+              "type": ["object", "null"]
+            }
+          }
+        },
+        "egress": {
+          "type": ["object", "null"],
+          "additionalProperties": false,
+          "properties": {
+            "extraPorts": {
+              "description": "Additional outbound TCP ports, to ANY destination - ports and not destinations, because a NetworkPolicy cannot express a hostname. DNS is always allowed and has no switch. Without an entry here an outbound port the chart does not already derive is blocked, which is the cap's whole purpose and also its upgrade risk.",
+              "type": ["array", "null"],
+              "items": {
+                "type": "integer"
+              }
+            }
+          }
+        }
+      }
+    },
     "scaleDown": {
       "type": "boolean"
     },