minecraft-router: strict values.schema.json and null-safe hardening

No ingress gate: this chart has no Ingress at all (clients reach it via a
NodePort), and ingress.domain appears neither in its templates nor in its
values.

1. values.schema.json (#68): additionalProperties: false on every
   chart-owned object level, including the entries of the mappings list,
   where domain and internalUrl are required.

2. Null-safety for hardening, probes and resources (#99). Two things a
   rebuilt default probe must not lose, both verified:
   - the API port is addressed by NAME ("api-port"), so the probe keeps
     working when server.apiPort is overridden.
   - mc-router still has no /health endpoint in 1.46.4, so GET /routes is
     the health signal, and the "Accept: application/json" header belongs
     to that request.

   The pod context keeps pinning uid/gid 10000 even though the image
   declares USER 65532 since 1.46.0, so the runtime identity does not
   silently change with the base image.

mappings stays deliberately not null-safe: the chart fails loudly on a
missing or empty routing table, which is the loud class #99 excludes - a
router without routes is not operable and has no sensible default.

Rendering with normal values is byte-identical to 2.0.0.

minecraft-router/Chart.yaml

@@ -5,7 +5,7 @@ icon: https://avatars.githubusercontent.com/u/988985
 
 type: application
 
-version: 2.0.0+up1.46.4
+version: 3.0.0+up1.46.4
 appVersion: "1.46.4"
 
 maintainers: