Bring minecraft-server up to the chart style guidelines (1.0.0+upjava8)

Stage 2 of the Fleet migration for minecraft-server. Major bump: runtime
behaviour changes (probes, hardening) and the values interface breaks
(resource renames, strict schema).

Two real bugs first:
- The container declared port 35565 while the Service targeted 25565. It
  only worked because targetPort was numeric. Both are now server.port
  (25565) and the Service targets the named port.
- The download-serverpack init container was guarded by the map
  .Values.curseforgeServerpack instead of .enabled, so it rendered for
  every release and silently no-opped on an empty wget URL.

Conventions:
- Resources renamed to <release>-<chart>-<kind>, templates to
  <app>.<kind>.yaml. The PVC deliberately keeps its historical name -
  renaming it would provision a new, empty volume and orphan the worlds.
- Probes (liveness/readiness/startup) via the image's own mc-health, so
  Ready means the server answers a server-list ping. Startup budget 20 min.
- Hardened, values-configurable security contexts: non-root uid 1000,
  read-only root filesystem with an emptyDir at /tmp, all caps dropped.
- Resources from values with the limitFactor helper; an unset memory
  request is derived from the JVM heap so the two cannot drift apart.
- Additive env block rendered through tpl, pinned init image, storage
  class as a value, RCON wiring only when actually enabled.
- curseforge/ftb/curseforgeServerpack are now mutually exclusive.
- minecraft.version is pinned to the Java line instead of LATEST.
- The mc-router auto-discovery annotation is gone; the service type it
  implicitly switched is now the explicit value server.service.type.

Schema pilot (#68): values.schema.json with additionalProperties false on
every chart-owned level, rejecting all three known dead keys.

README.md

@@ -13,7 +13,7 @@ Collection of some self-made helm-charts. Each top-level directory is a standalo
 | `homeassistant` | Home Assistant | StatefulSet, has `NOTES.txt` and Helm tests |
 | `matrix-synapse` | Matrix Synapse | StatefulSet plus an nginx delegation Deployment/Service |
 | `minecraft-router` | itzg/mc-router | Deployment + routing ConfigMap + NodePort Service (TCP only, no ingress); `mappings` is a required value |
-| `minecraft-server` | itzg/minecraft-server | StatefulSet + PVC + NodePort Service + init-script ConfigMap (no ingress); pre-existing chart, still on its legacy conventions. Published once per Java line (`appVersion: java8` / `java17` / `java21`) — the image tag comes from `.Chart.AppVersion`, so the Java line is chosen by picking the chart version |
+| `minecraft-server` | itzg/minecraft-server | StatefulSet + PVC + Service + init-script ConfigMap (no ingress); service type is a value (`ClusterIP` by default, routed via `minecraft-router`). Published once per Java line (`appVersion: java8` / `java17` / `java21`) — the image tag comes from `.Chart.AppVersion`, so the Java line is chosen by picking the chart version, and `minecraft.version` ships a default matching that line. First chart with a strict `values.schema.json` (pilot, #68) |
 | `outline` | Outline | StatefulSet, separate DB/Redis secrets |
 | `paperless-ngx` | Paperless-ngx | Largest chart: consume CronJob, SMB-connector PV/PVC, pre/post-consumption scripts ConfigMap |
 | `patchmon` | PatchMon | Two Deployments (frontend + backend), OIDC secret |