Import minecraft-router chart unchanged (Fleet migration stage 1)

Takes the existing mc-router chart over from cluster-config as-is so the
deployment can move to Fleet without any change to the rolled-out state.
Convention alignment follows in stage 2, the app update in stage 3.

The only deviation from "unchanged": Chart.yaml carried name:
minecraft-server (copy-paste from the sister chart). The publish job pushes
by the glob <directory>-*.tgz while helm package names the archive after the
Chart.yaml name, so without this correction the push finds no file.

Version 0.1.1+up1.25.1 - chart semver stays at 0.1.1, the +up suffix is repo
policy and does not affect rendering.

Also wires up CI: publish workflow, change-app-version choice list,
install-test values (CI-only node-port override, since 25565 is outside the
k3d default range) and the README chart table.

README.md

@@ -12,6 +12,7 @@ Collection of some self-made helm-charts. Each top-level directory is a standalo
 | `gotenberg` | Gotenberg | Deployment + Service only (no ingress) |
 | `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); pre-existing chart, still on its legacy conventions |
 | `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 |