Minecraft-router chart: naming scheme, hardening, probes, values interface

Stage 2 of the Fleet migration for minecraft-router: bring the chart up to the
repo style guidelines. Chart 0.1.1+up1.25.1 -> 1.0.0+up1.25.1 (major: resource
renames, mappings becomes required, probes and security hardening change the
runtime behavior; appVersion unchanged).

- Resources renamed to {{ .Release.Name }}-{{ .Chart.Name }}-<kind>, templates
  to <chart>.<kind>.yaml; the deployment label now matches its own selector.
- mappings is required and must not be empty (the old default rendered
  "<nil>": "<nil>:25565"); every entry needs domain and internalUrl.
- Ports come from values: server.port (router listen port, also passed as
  --port), server.backendPort (default backend port, overridable per mapping),
  server.apiPort (--api-binding, used by the probes). Defaults stay 25565 /
  25565 / 8080, server.outwardPort keeps its 25565 default and comment.
- _helpers.tpl added (resources/limitFactor and replicas/scaleDown helpers),
  resources come from values, no CPU limit.
- replicas value plus the chart-global scaleDown flag.
- Additive env block rendered through tpl (value / secretKeyRef /
  configMapKeyRef).
- Values-configurable securityContext.pod / .container with hardened defaults:
  non-root uid/gid 10000, readOnlyRootFilesystem, no privilege escalation, all
  capabilities dropped.
- Liveness, readiness and startup probes on the mc-router API: GET /routes with
  an "Accept: application/json" header (the API router matches on that header
  and answers 404 without it).
- icon added to Chart.yaml.
- CI fixture supplies mappings; README chart table entry updated.

minecraft-router/Chart.yaml

@@ -1,24 +1,12 @@
 apiVersion: v2
 name: minecraft-router
 description: A Helm chart for deploying a itzg/mc-router
+icon: https://avatars.githubusercontent.com/u/988985
 
-# A chart can be either an 'application' or a 'library' chart.
-#
-# Application charts are a collection of templates that can be packaged into versioned archives
-# to be deployed.
-#
-# Library charts provide useful utilities or functions for the chart developer. They're included as
-# a dependency of application charts to inject those utilities and functions into the rendering
-# pipeline. Library charts do not define any templates and therefore cannot be deployed.
 type: application
 
-# This is the chart version. This version number should be incremented each time you make changes
-# to the chart and its templates, including the app version.
-# Versions are expected to follow Semantic Versioning (https://semver.org/)
-version: 0.1.1+up1.25.1
-
-# This is the version number of the application being deployed. This version number should be
-# incremented each time you make changes to the application. Versions are not expected to
-# follow Semantic Versioning. They should reflect the version the application is using.
-# It is recommended to use it with quotes.
+version: 1.0.0+up1.25.1
 appVersion: "1.25.1"
+
+maintainers:
+  - name: jklein