Fix build and cut image size via multi-stage rewrite (2.45GB -> 1.27GB)

Two unrelated pre-existing compile failures surfaced on a fresh build
(both from unpinned `ADD <git-url>` sources drifting against current
Debian's GCC/Boost):

- Debian's libboost-all-dev is missing #include <utility> in
  awaitable.hpp, which current GCC/libstdc++ no longer pulls in
  transitively, breaking UHD's C++20-coroutine-mode rpclib build with
  "'exchange' is not a member of 'std'". Patched the header directly.
- SoapyUHD pins itself to C++14 and is missing a lexical_cast include in
  two files; current UHD's public headers need C++17 (std::optional).
  Bumped SoapyUHD's CMAKE_CXX_STANDARD to 17 and added the missing
  #include <boost/lexical_cast.hpp> in both files.

Also split the single-stage Dockerfile (which kept the entire build
toolchain - build-essential, cmake, doxygen, libboost-all-dev,
python3-dev/numpy/scipy, plus every /tmp/sources/* source and build tree -
in the final image) into a builder stage and a minimal final stage that
only installs real runtime packages (derived via `ldd` on every compiled
binary/module, not guessed) and COPYs over the compiled artifacts.

Verified: SSH, sdrplay_apiService, and all three SoapySDR modules
(remote/sdrplay/uhd) load correctly; signal handling still exits 143 on
docker stop.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NiNnj78HGx1KWyCCo39HSz

Dockerfile

@@ -11,6 +11,12 @@ RUN apt-get update && \
     gpsd gpsd-clients \
     && rm -rf /var/lib/apt/lists/*
 
+# Debian's libboost-all-dev is missing an #include <utility> in awaitable.hpp that current
+# GCC/libstdc++ no longer pulls in transitively, breaking any C++20-coroutine-mode compile
+# (e.g. UHD's rpclib) with "'exchange' is not a member of 'std'". Patch it in until Debian's
+# packaged Boost picks up the upstream fix.
+RUN sed -i '/#define BOOST_ASIO_AWAITABLE_HPP/a #include <utility>' /usr/include/boost/asio/awaitable.hpp
+
 # ----------------------------------------------------------------------------------------------------------------------------------------
 # Build from sources
 # ----------------------------------------------------------------------------------------------------------------------------------------
@@ -56,6 +62,13 @@ RUN /usr/local/bin/uhd_images_downloader -t b2xx
 
 # SoapyUHD
 ADD https://github.com/pothosware/SoapyUHD.git /tmp/sources/SoapyUHD
+# SoapyUHDDevice.cpp and UHDSoapyDevice.cpp both use boost::lexical_cast without including it
+# directly, relying on a transitive include from a UHD header that no longer provides it.
+RUN sed -i '/#include <cctype>/i #include <boost/lexical_cast.hpp>' /tmp/sources/SoapyUHD/SoapyUHDDevice.cpp
+RUN sed -i '/#include <boost\/weak_ptr.hpp>/a #include <boost/lexical_cast.hpp>' /tmp/sources/SoapyUHD/UHDSoapyDevice.cpp
+# SoapyUHD pins itself to C++14, but current UHD's public headers (e.g. rfnoc/register_iface.hpp)
+# use std::optional, which needs C++17+. Bump the standard it's built with to match.
+RUN sed -i 's/set(CMAKE_CXX_STANDARD 14)/set(CMAKE_CXX_STANDARD 17)/' /tmp/sources/SoapyUHD/CMakeLists.txt
 WORKDIR /tmp/sources/SoapyUHD/build
 RUN cmake ../
 RUN make -j$(nproc)
@@ -82,15 +95,39 @@ RUN make install -j$(nproc)
 RUN ldconfig
 
 # ----------------------------------------------------------------------------------------------------------------------------------------
-# Add user
+# Minimal runtime image: everything above is a full build toolchain (compilers, cmake,
+# -dev packages, full source trees under /tmp/sources) that's only needed to produce the
+# compiled artifacts, not to run them. Only the actual runtime pieces get copied out below.
+# ----------------------------------------------------------------------------------------------------------------------------------------
+FROM jayfield/debian-baseimage AS final
+
+# Runtime-only equivalents of build_base's/build's -dev packages, derived by `ldd`-ing every
+# compiled binary/module in the build stage and mapping the non-/usr/local .so's back to the
+# packages that own them (see git history for the exact command). Anything not listed here
+# comes in automatically as a transitive apt dependency of these.
+RUN apt-get update && \
+    apt-get -y install --no-install-recommends \
+    openssh-server gpsd gpsd-clients \
+    libavahi-client3 libusb-1.0-0 \
+    libboost-chrono1.74.0 libboost-program-options1.74.0 libboost-serialization1.74.0 libboost-thread1.74.0 \
+    && rm -rf /var/lib/apt/lists/*
+
 RUN useradd -m jens -p jens -s /usr/bin/bash
 RUN echo jens:change_me | chpasswd
 RUN echo root:root4me | chpasswd
 
-
 WORKDIR /home/jens
 RUN touch .Xauthority
 
+# Compiled libraries/binaries (SoapySDR, SoapyRemote, UHD + its downloaded FPGA images,
+# SoapyUHD, SoapySDRPlay) and the SDRplay API service + its udev rules for device recognition.
+COPY --from=build /usr/local /usr/local
+COPY --from=build /opt/sdrplay_api /opt/sdrplay_api
+COPY --from=build /etc/udev/rules.d/66-sdrplay.rules /etc/udev/rules.d/66-sdrplay.rules
+COPY --from=build /etc/udev/hwdb.d/20-sdrplay.hwdb /etc/udev/hwdb.d/20-sdrplay.hwdb
+RUN ldconfig
+ENV UHD_MODULE_PATH=/usr/local/lib/uhd/modules
+
 # Copy scripts and configs
 ENV SCRIPTS_HOME=/opt/scripts
 ENV PATH=${PATH}:${SCRIPTS_HOME}