Add K8s deployment for OCI (aarch64) and make deploy/deploy-oci targets

- K8s manifests: namespace, PVC (local-path 2Gi), deployment, service, ingress
- Ingress: repo-vis.oci.euphon.net with Let's Encrypt TLS via traefik
- Cross-compile aarch64-unknown-linux-musl for OCI ARM64 host
- make deploy: local Docker (x86_64)
- make deploy-oci: SCP binary + web dist to OCI, native docker build, k3s import
- Dockerfile accepts MUSL_TARGET build arg for multi-arch support

k8s/pvc.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: repo-vis-data
+  namespace: repo-vis
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 2Gi