run backend in docker container

Dockerfile

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+# --- STAGE 1: Build the native OCaml binary ---
+FROM ocaml/opam:debian-12-ocaml-5.4 AS builder
+USER opam
+WORKDIR /app
+COPY --chown=opam:opam dune-project ./
+RUN opam update && opam install -y dune dream
+COPY --chown=opam:opam . .
+RUN opam exec -- dune build bin/main.exe
+
+# --- STAGE 2: Lightweight runtime environment ---
+FROM debian:12-slim
+WORKDIR /app
+
+# Install native system dependencies and a minimal TeX Live profile
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libssl3 \
+    libev4 \
+    ca-certificates \
+    #     texlive-latex-base \
+    #     texlive-latex-recommended \
+    #     texlive-fonts-recommended \
+    #     # tlmgr is the TeX Live package manager; we use it to grab chess assets
+    #     texlive-games \ 
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy the compiled native OCaml binary from Stage 1
+COPY --from=builder /app/_build/default/bin/main.exe ./server
+
+EXPOSE 8080
+CMD ["./server"]