feat!: NetworkPolicy in the NodePort and game-server charts, on by default

garage, minecraft-router, minecraft-server, samba, teamspeak-server,
satisfactory. One major each. These are the charts the plan said to leave for
last, and they earned it - three of them changed the convention rather than
just consuming it.

GARAGE is the clearest illustration after keycloak. Its four ports split three
ways: s3 and web are RESTRICTED by source (no probe touches them), admin is the
probe path and stays open inside the cluster - which is uncomfortable, because
admin is also the admin API, and that is said out loud instead of glossed - and
rpc gets the narrowest rule the object can express, a podSelector with no
namespaceSelector. All four numbers come from garage.settings.

MINECRAFT-SERVER is the tightest policy in the repository, and the reason is
worth knowing: all three of its probes are EXEC probes, which put no packet on
the network, so no port has to stay open for the kubelet and no probeSources
value is needed at all. RCON and metrics are restricted outright. The game port
has two branches rendered from the same value the Service reads -
server.service.type NodePort means players arrive from the internet and the
rule must be open; anything else means the only path is in-cluster, so the rule
is restricted and the router's namespace has to be in allowedNamespaces.

MINECRAFT-ROUTER derives its egress from the routing table instead of guessing:
server.backendPort plus the "port" override of every mapping that sets one. Add
a backend on a non-standard port and the policy follows. What it cannot express
is the destination - mappings name hosts, and this object matches no hostname -
so the rule is wider than the routing table, and that is written down.

SATISFACTORY gets policyTypes: [Ingress] and no egress section, and the second
half of the reason is the deciding one. Steam's content delivery is not a
pinnable port set (SteamCMD over TCP 80/443/27015-27050, master servers over
UDP 27000-27100 and 4380, changed by Valve, re-downloaded on every update) -
and this is the ONE chart with no install-test at all, because the image is
multiple GB and the first start pulls over 10GB. An egress cap here would be
the only one in the sweep with no empirical check behind it, on the chart whose
correct port set is least knowable.

SAMBA and TEAMSPEAK-SERVER carry the NodePort lesson explicitly: the rules name
445/139 and the pod's voice and file-transfer ports, never the NodePorts, and
teamspeak's file is explicit that its pod port and NodePort happening to share a
number is a coincidence of its values rather than a pattern to copy. Teamspeak's
voice rule is UDP, and the file says why that matters: a TCP rule on the same
number is accepted, looks complete, and drops every voice packet.

THREE THINGS THE CHECKS CAUGHT WHILE THIS BATCH WAS WRITTEN, all of them real:

  - minecraft-server's RCON rule named a port the pod does not declare. The
    containerPort is gated on server.rcon.enabled and the rule was not, so
    assertion 2 rejected it. The rule now carries the same gate.
  - samba and satisfactory would have shipped allowedNamespaces and
    probeSources values that reach NO rule - every one of their inbound rules
    is open to any source. A value that silently does nothing is worse than one
    that is absent, because it reads as a control, so both are gone from those
    two charts and from their schemas, with the reason in values.yaml.
    teamspeak-server loses probeSources for the same reason and keeps
    allowedNamespaces, which its web-query rule uses.
  - the policy templates no longer declare template variables they do not use.
    samba keeps one, satisfactory none.

Part of #5

samba/values.yaml

@@ -96,3 +96,49 @@ samba:
           - SETUID
 
   storageClass: longhorn
+
+# ---------------------------------------------------------------------------
+# NetworkPolicy (Gitea #5). On by default. The reference implementation with
+# the full reasoning is template-chart; the convention is in README, "Chart
+# style guidelines", and the operator's view on this chart's wiki page.
+# ---------------------------------------------------------------------------
+networkPolicy:
+  # THERE IS ONLY ONE VALUE HERE BESIDES enabled, AND THAT IS DELIBERATE.
+  # Both of this chart's inbound rules are open to any source (see below), so
+  # neither allowedNamespaces nor probeSources would reach a rule - and a value
+  # that silently does nothing is worse than a value that is absent: it reads
+  # as a control. If a source restriction is ever wanted here it needs a rule
+  # to attach to first.
+  #
+  # WHAT THIS POLICY ALLOWS: inbound 445 and 139 - the POD ports - open to any
+  # source, and outbound nothing but DNS.
+  #
+  # BOTH INBOUND RULES ARE OPEN ON PURPOSE. The ports are published as
+  # NodePorts and the clients are machines on the LAN; after NodePort
+  # masquerading the source address is a cluster node, so a source selector
+  # could only be a list of node IPs - a restriction in appearance and a
+  # maintenance trap in fact. 445 is also the probe port.
+  #
+  # AND THE NUMBERS ARE 445 AND 139, NOT samba.smbNodePort AND
+  # samba.netbiosNodePort. A NetworkPolicy is evaluated at the pod's interface
+  # after kube-proxy has translated the NodePort, so the NodePort numbers would
+  # match nothing while looking strict - and would block every client.
+  #
+  # Not covered, and it does not matter here: the NetBIOS name-service
+  # broadcasts on 137/138 UDP are not published by this chart's Service at all,
+  # and clients reach the share by address rather than by browse list.
+  enabled: true
+  egress:
+    # Additional outbound TCP ports. DNS (UDP and TCP 53) is always allowed and
+    # has no switch - a knob whose only other setting breaks every name lookup
+    # in the pod is a trap, not a feature.
+    #
+    # PORTS, NOT DESTINATIONS, and that is a limit of the object rather than
+    # laziness: a NetworkPolicy matches CIDRs and selectors and never hostnames,
+    # so "only to the database host" cannot be written at all. Each entry
+    # permits its port to ANY destination. What the cap still buys is real: a
+    # compromised pod cannot open arbitrary outbound connections.
+    #
+    # A domain-joined Samba needs Kerberos (88) and LDAP (389 or 636) here. A
+    # standalone one needs nothing.
+    extraPorts: []