Add Dockerfile for containerized deployment

Two-stage Alpine build, plain HTTP on :8080 behind mc-proxy L7.
Follows mcdoc pattern — no USER/VOLUME directives (rootless podman).

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

Dockerfile

@@ -0,0 +1,24 @@
+FROM golang:1.25-alpine AS builder
+
+ARG VERSION=dev
+
+RUN apk add --no-cache git
+
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" -o mcq ./cmd/mcq
+
+FROM alpine:3.21
+
+RUN apk add --no-cache ca-certificates tzdata
+
+COPY --from=builder /build/mcq /usr/local/bin/mcq
+
+WORKDIR /srv/mcq
+EXPOSE 8080
+
+ENTRYPOINT ["mcq"]
+CMD ["server", "--config", "/srv/mcq/mcq.toml"]