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

Dockerfile

@@ -11,7 +11,8 @@ FROM alpine:3.21
 RUN apk add --no-cache git ca-certificates
 
 WORKDIR /app
-COPY server/target/x86_64-unknown-linux-musl/release/repo-vis-server ./
+ARG MUSL_TARGET=x86_64-unknown-linux-musl
+COPY server/target/${MUSL_TARGET}/release/repo-vis-server ./
 COPY --from=frontend /build/dist ./web/dist/
 
 ENV PORT=8080