build(routing): Dockerfile + CD workflow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile.routing

@@ -0,0 +1,30 @@
+# syntax=docker/dockerfile:1
+
+# ── Build stage ───────────────────────────────────────────────────────────────
+FROM golang:1.26-bookworm AS builder
+
+ARG VERSION=dev
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
+    go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" \
+    -o /out/routing ./cmd/routing
+
+# ── Runtime stage ─────────────────────────────────────────────────────────────
+FROM gcr.io/distroless/base-debian12
+
+COPY --from=builder /out/routing /usr/local/bin/routing
+COPY config/ /app/config/
+
+ENV SUPERVISOR_CONFIG_DIR=/app/config/supervisor
+ENV ROUTING_PORT=3210
+
+EXPOSE 3210
+
+USER 65532:65532
+
+ENTRYPOINT ["/usr/local/bin/routing"]