Add Dockerfile and Makefile for building and generating Protobuf code

services/data_service/Dockerfile

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+# Stage 1: Builder
+FROM golang:latest AS builder
+
+WORKDIR /app
+
+# Copy go mod and download deps
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source
+COPY . .
+
+# Build binary
+RUN CGO_ENABLED=0 GOOS=linux go build -o /data_service ./services/data_service/cmd
+
+# Stage 2: Runner
+FROM debian:bullseye-slim
+
+# Minimal setup
+RUN apt-get update && apt-get install -y ca-certificates && rm -rf /var/lib/apt/lists/*
+
+# Copy binary
+COPY --from=builder /data_service /usr/local/bin/data_service
+
+ENTRYPOINT ["data_service"]