Add MUDCraft Minecraft server infrastructure

- Purpur 1.21.4 server via itzg/docker-minecraft-server (java21)
- StatefulSet with 3 PVCs: worlds (20Gi), plugins (5Gi), logs (5Gi)
- Aikar G1GC JVM flags, 6GB heap (sized for Legion's 15GB RAM)
- Postgres: mudcraft database + user in existing platform/postgres
- RCON secret + DB password via ExternalSecret → Vault
- Traefik TCP entrypoint on port 25565 for mudcraft.nook.family
- mudcraft namespace via Terraform
- Argo CD app watching k8s/mudcraft/

servers/legion/k8s/mudcraft/external-secrets.yaml

@@ -0,0 +1,23 @@
+---
+apiVersion: external-secrets.io/v1beta1
+kind: ExternalSecret
+metadata:
+  name: mudcraft-secrets
+  namespace: mudcraft
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    name: vault
+    kind: ClusterSecretStore
+  target:
+    name: mudcraft-secrets
+    creationPolicy: Owner
+  data:
+    - secretKey: db-password
+      remoteRef:
+        key: secret/data/legion-db
+        property: mudcraft_db_password
+    - secretKey: rcon-password
+      remoteRef:
+        key: secret/data/mudcraft
+        property: rcon_password