Deploy sgardd to rift and add persistent remote config.

Deployment: Dockerfile + docker-compose for sgardd on rift behind mc-proxy
(L4 SNI passthrough on :9443, multiplexed with metacrypt gRPC). TLS via
Metacrypt-issued cert, SSH-key auth.

CLI: `sgard remote set/show` saves addr, TLS, and CA path to
<repo>/remote.yaml so push/pull work without flags.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

deploy/docker/Dockerfile

@@ -0,0 +1,30 @@
+# Build stage
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+ARG VERSION=dev
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /sgardd ./cmd/sgardd
+
+# Runtime stage
+FROM alpine:3.21
+
+RUN apk add --no-cache ca-certificates tzdata \
+    && adduser -D -h /srv/sgard sgard
+
+COPY --from=builder /sgardd /usr/local/bin/sgardd
+
+VOLUME /srv/sgard
+EXPOSE 9473
+
+USER sgard
+
+ENTRYPOINT ["sgardd", \
+    "--repo", "/srv/sgard", \
+    "--authorized-keys", "/srv/sgard/authorized_keys", \
+    "--tls-cert", "/srv/sgard/certs/sgard.pem", \
+    "--tls-key", "/srv/sgard/certs/sgard.key"]