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/ingress.yaml

@@ -0,0 +1,23 @@
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: repo-vis
+  namespace: repo-vis
+  annotations:
+    traefik.ingress.kubernetes.io/router.tls.certresolver: le
+spec:
+  ingressClassName: traefik
+  rules:
+    - host: repo-vis.oci.euphon.net
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: repo-vis
+                port:
+                  number: 80
+  tls:
+    - hosts:
+        - repo-vis.oci.euphon.net