perf: faster builds, leaner daemon, smoother install/run (0.9.20)

Reuse libcstcore.a for tests with -MMD incremental deps; idle-backoff the
parliament seat loop; defer curl init and cache settings; add systemd helper.

Co-authored-by: Cursor <cursoragent@cursor.com>

CMakeLists.txt

@@ -400,17 +400,13 @@ if(CST_BUILD_WEBUI)
   list(APPEND _CST_CORE_TESTS test_webui)
 endif()
 foreach(t ${_CST_CORE_TESTS})
-  add_executable(${t} tests/${t}.c ${CST_CORE_SOURCES})
-  # The core now contains src/web_md.c, which needs sashidown's header and
-  # archive exactly like the Makefile build does.
+  # Link the shared cstcore archive instead of recompiling every core .c.
+  add_executable(${t} tests/${t}.c)
   target_include_directories(${t} PRIVATE include "${CJSON_DIR}" "${SD_DIR}/include")
   target_compile_definitions(${t} PRIVATE _GNU_SOURCE)
-  target_link_libraries(${t} PRIVATE
-    "${SASHIDOWN_A}" CURL::libcurl Threads::Threads)
+  target_link_libraries(${t} PRIVATE cstcore)
   add_dependencies(${t} sashidown)
-  if(NOT WIN32)
-    target_link_libraries(${t} PRIVATE m)
-  else()
+  if(WIN32)
     target_link_libraries(${t} PRIVATE ws2_32 crypt32 secur32 bcrypt advapi32 user32)
   endif()
   cst_win_exe(${t})