feat!: NetworkPolicy in six more charts, on by default

bentopdf, apache-tika, gotenberg, rss-bridge, searxng, ytdlp-web-player. One
major each, networkPolicy.enabled defaults to true.

Three of them differ from the simple case in ways worth naming:

GOTENBERG gets DNS-only egress as a deliberate, documented trade. It drives a
headless Chromium, and 3000 is its probe port - so it is reachable from the
whole cluster by default, and an egress rule for 80/443 would turn a service
anyone can POST to into a way of fetching arbitrary URLs. The price is the
remote-asset half of HTML conversion: inline content converts, images the page
would have fetched silently do not. That degrades a PDF instead of failing a
pod, so nothing alerts on it, which is why it is in the template header, in
values.yaml and in NOTES.txt, with extraPorts: [80, 443] named as the knowing
opt-in.

RSS-BRIDGE, SEARXNG and YTDLP-WEB-PLAYER get the open internet on their web
ports, because reaching other people's servers IS the application and this
object cannot name a host. Said plainly in each, so none of them reads
stricter than it is. What the cap still buys is real: no other outbound port,
so a compromised pod reaches no database, no mail server and no SSH anywhere.

APACHE-TIKA and GOTENBERG render no Ingress - their consumers are other pods,
in other namespaces here - so neither gets an ingressController value and both
say in NOTES.txt that narrowing probeSources means listing the consumers'
namespaces in allowedNamespaces in the same change, or extraction and
conversion stop.

YTDLP-WEB-PLAYER names the gap this convention has: its oauth2-proxy subchart
renders its own Deployment with its own labels and ships no policy, so with the
proxy enabled the pod that actually faces the Ingress is unrestricted in both
directions. Nothing in this chart can change that - an upstream chart is
consumed as it comes - so it is written down instead.

ci/outline/test-values.yaml gains egress.extraPorts: [5556]. The CI dex runs
there rather than on 443, and Outline fetches the discovery document at boot -
so this is the chart's documented escape hatch used for exactly the case it was
written for, and the one place in the repo where the cap's upgrade risk is
actually exercised.

Part of #5

gotenberg/values.schema.json

@@ -9,6 +9,43 @@
       "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"
+          }
+        },
+        "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"
     },