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

apache-tika/templates/apache-tika.networkpolicy.yaml

@@ -0,0 +1,149 @@
+{{- /*
+NetworkPolicy for apache-tika (Gitea #5).
+
+Apache Tika here is a cluster-internal service: the chart creates no Ingress at
+all, and its only consumers are other pods - paperless-ngx points at
+http://<service>.<namespace>.svc.cluster.local for text extraction.
+
+THAT MAKES THE SOURCE QUESTION THE INTERESTING ONE, AND IT HAS AN AWKWARD
+ANSWER. 9998 is the port all three probes address, so it cannot be restricted
+by source without the worker node's IP - and this chart's consumers live in
+OTHER namespaces (paperless-cmk, paperless-jk, paperless-tb in this cluster).
+So an operator who narrows probeSources has to list those namespaces in
+allowedNamespaces in the same breath, or every document extraction stops. That
+is written into values.yaml and NOTES.txt rather than left to be discovered.
+
+Egress is DNS only. Tika extracts text from documents it is handed; it fetches
+nothing, and a text extractor that can reach the internet is a worse thing to
+hand an untrusted document to.
+
+WHAT THIS OBJECT IS: a ceiling on reachability, not an authentication layer.
+Only the ports declared below are reachable at all - whatever else the process
+binds, now or after the next app update, is blocked without anyone having to
+notice it exists.
+
+WHAT IT IS NOT:
+  - EGRESS IS COARSE. A NetworkPolicy matches CIDRs and selectors and NEVER
+    hostnames, so "only to the database host" cannot be expressed at all. This
+    cluster's CNI is Canal (Flannel plus Calico for policy) and has no FQDN
+    rule; Calico's GlobalNetworkSet could express one but would bind this chart
+    to Calico, the same argument that kept implementation-specific objects out
+    of the Gateway-API sweep (#114). Each egress rule therefore permits its
+    PORT to any destination.
+  - NOT A BOUNDARY WHERE THE CNI DOES NOT ENFORCE ONE. An unenforced policy is
+    accepted by the API server and filters nothing, so everything reads as
+    configured while nothing is filtered.
+  - THE REASONING IS IN TEMPLATE COMMENTS, not in "#" comments: those are part
+    of the rendered object, travel into the cluster and appear in every release
+    diff. ci/run-networkpolicy-test.sh fails on a rendered "#".
+
+THE PORT NUMBERS BELOW ARE POD PORTS, NEVER NODEPORTS. A NetworkPolicy is
+evaluated at the pod's network interface, after kube-proxy has already
+translated a NodePort to the targetPort, so a NodePort number here would match
+nothing while looking strict - and, being the only rule for that port, would
+block every inbound connection instead. ci/run-networkpolicy-test.sh asserts
+every port here against the containerPorts of the pod spec this policy
+selects.
+*/ -}}
+{{- if .Values.networkPolicy.enabled }}
+{{- $np := .Values.networkPolicy }}
+{{- $ns := .Release.Namespace }}
+{{- $probeSources := $np.probeSources | default list }}
+{{- $allowedNs := $np.allowedNamespaces | default list }}
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
+  labels:
+    app: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
+spec:
+  {{- /*
+  Selects the Deployment's pods. ci/run-networkpolicy-test.sh fails if
+  this matches no pod spec of the same render - which is the mistake that
+  would otherwise leave a policy in the namespace filtering nothing, and
+  its usual cause is a label renamed in the workload template.
+  */}}
+  podSelector:
+    matchLabels:
+      app: {{ .Release.Name }}-{{ .Chart.Name }}-deployment
+  policyTypes:
+    - Ingress
+    {{- /*
+    Egress is listed because there is something real to restrict: Tika extracts
+    text from documents it is handed and fetches nothing of its own, so DNS is the
+    only rule. A text extractor that can reach the internet is a worse thing to
+    hand an untrusted document to.
+    */}}
+    - Egress
+  ingress:
+    {{- /*
+    9998 - the only port this pod declares, the one the Service forwards 80 to, and
+    the one all three probes address. The probe path.
+    */}}
+    - ports:
+        - protocol: TCP
+          port: 9998
+      {{- if $probeSources }}
+      {{- /*
+      RESTRICTED, because the operator supplied probeSources. The kubelet's probes
+      come from the IP of the WORKER NODE running the pod, so that address has to be
+      in the list or the pod never becomes Ready - and a pod that is never Ready
+      reads as a broken application rather than as a policy.
+
+      NO ingress controller is added here, because this chart renders no Ingress: its
+      consumers are other pods, and they have to be named in allowedNamespaces.
+      */}}
+      from:
+        - namespaceSelector:
+            matchLabels:
+              {{- /*
+              Set by Kubernetes itself on every namespace (>= 1.21), so this needs no
+              labelling work on a namespace this chart does not own.
+              */}}
+              kubernetes.io/metadata.name: {{ $ns }}
+        {{- range $allowedNs }}
+        - namespaceSelector:
+            matchLabels:
+              kubernetes.io/metadata.name: {{ . | quote }}
+        {{- end }}
+        {{- range $probeSources }}
+        - ipBlock:
+            cidr: {{ . | quote }}
+        {{- end }}
+      {{- else }}
+      {{- /*
+      NO "from" SELECTOR, WHICH MEANS OPEN - deliberately, and only inside the
+      cluster, because this port carries no NodePort. The alternative was to guess
+      the worker node CIDRs, and a wrong guess blocks every kubelet probe: the pod
+      stays un-Ready, the rollout times out, and the cause looks like the
+      application. An empty "from: []" would be worse than either - it allows
+      everything too, but while reading as a restriction. Narrow it with
+      networkPolicy.probeSources.
+      */}}
+      {{- end }}
+  egress:
+    {{- /*
+    DNS, unconditionally. There is no value to switch this off, and that is
+    deliberate: a knob whose only other setting breaks every name lookup in
+    the pod is a trap and not a feature.
+    */}}
+    - ports:
+        - protocol: UDP
+          port: 53
+        - protocol: TCP
+          port: 53
+    {{- with $np.egress }}
+    {{- with .extraPorts }}
+    {{- /*
+    Ports only, to any destination - see the header. This is the operator's
+    escape hatch from the egress cap, and the only alternative to switching
+    the whole policy off.
+    */}}
+    - ports:
+        {{- range . }}
+        - protocol: TCP
+          port: {{ int . }}
+        {{- end }}
+    {{- end }}
+    {{- end }}
+{{- end }}