fix(dwg): build libredwg from source (not in any apt repo)

Multi-stage build: compile libredwg 0.13.3 in builder stage,
copy only dwg2dxf binary + libs to final slim image.

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

dwg2dxf-api/Dockerfile

@@ -1,11 +1,31 @@
-FROM ubuntu:24.04
-
-# Enable universe repo (libredwg-tools lives there)
-RUN sed -i 's/Components: main/Components: main universe/' /etc/apt/sources.list.d/ubuntu.sources
+FROM ubuntu:24.04 AS builder
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-        python3 python3-pip libredwg-tools && \
+        build-essential autoconf automake libtool pkg-config \
+        wget ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
+
+# Build libredwg from source (not available in apt repos)
+ARG LIBREDWG_VERSION=0.13.3
+RUN wget -q "https://github.com/LibreDWG/libredwg/releases/download/${LIBREDWG_VERSION}/libredwg-${LIBREDWG_VERSION}.tar.xz" && \
+    tar xf "libredwg-${LIBREDWG_VERSION}.tar.xz" && \
+    cd "libredwg-${LIBREDWG_VERSION}" && \
+    ./configure --prefix=/usr/local --disable-static --disable-docs && \
+    make -j"$(nproc)" && \
+    make install
+
+# ---
+
+FROM ubuntu:24.04
+
+# Copy only the built binaries and libraries
+COPY --from=builder /usr/local/bin/dwg2dxf /usr/local/bin/
+COPY --from=builder /usr/local/lib/libredwg* /usr/local/lib/
+
+RUN ldconfig && \
+    apt-get update && \
+    apt-get install -y --no-install-recommends python3 python3-pip && \
     pip3 install --no-cache-dir --break-system-packages flask && \
     apt-get purge -y python3-pip && \
     apt-get autoremove -y && \