fix(boost): add compatibility for Boost.Process v1 API in Boost 1.89+

Boost 1.88 replaced Boost.Process with v2, breaking the v1 API.
Boost 1.89 restores v1 compatibility via <boost/process/v1.hpp>.

- Fail configuration if Boost 1.88 is detected
- Define FAIRMQ_BOOST_PROCESS_V1_HEADER for Boost >= 1.89
- Use conditional includes to select v1.hpp or process.hpp
- Add namespace aliases (bp, bp_this) for portable API access

fairmq/CMakeLists.txt

@@ -176,6 +176,9 @@ if(BUILD_FAIRMQ)
     FAIRMQ_HAS_STD_FILESYSTEM=${FAIRMQ_HAS_STD_FILESYSTEM}
     FAIRMQ_HAS_STD_PMR=${FAIRMQ_HAS_STD_PMR}
   )
+  if(FAIRMQ_BOOST_PROCESS_V1_HEADER)
+    target_compile_definitions(${target} PRIVATE FAIRMQ_BOOST_PROCESS_V1_HEADER)
+  endif()
   if(DEFINED FAIRMQ_CHANNEL_DEFAULT_AUTOBIND)
     # translate CMake boolean (TRUE, FALSE, 0, 1, OFF, ON) into C++ boolean literal (true, false)
     if(FAIRMQ_CHANNEL_DEFAULT_AUTOBIND)