Import minecraft-server chart for Fleet migration stage 1 (java8 line)

Imports the chart from cluster-config functionally unchanged, wires it into
the publish/validate/install-test pipelines and publishes it as the first of
three Java lines (0.4.0+upjava8).

The only deviation from the source chart is the chart-global scaleDown flag
plus a server.replicas value, following the satisfactory pattern: two of the
three servers stand at 0 replicas in the cluster, which the chart could not
express, and Fleet would otherwise start them on reconcile. The default
(scaleDown: false) still renders replicas: 1, so the rendering of the running
server is unchanged - verified byte-identical against the three real values
files for all three Java lines.

Known deficiencies (hardening, probes, naming scheme, hardcoded values,
missing icon, the misleading mc-router auto-discovery annotations) are left
untouched on purpose and are scheduled for stage 2.

README.md

@@ -13,6 +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 |
 | `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 |