Hub runtime: allocate port 8788, add Go skeleton and Docker deployment

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Dockerfile

@@ -0,0 +1,13 @@
+# Multi-stage build. docs/hub-api.md section 1: Go 1.25, static binary,
+# distroless runtime, one container on 192.168.20.13.
+FROM golang:1.25-alpine AS build
+WORKDIR /src
+COPY src/ ./
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags='-s -w' -o /out/hub .
+
+FROM gcr.io/distroless/static-debian12:nonroot
+COPY --from=build /out/hub /hub
+ENV HUB_PORT=8788
+EXPOSE 8788
+USER nonroot:nonroot
+ENTRYPOINT ["/hub"]