fix: set CMAKE_CXX_STANDARD before project() for correct Conan profile on Windows

conan_provider.cmake fires during project() via CMAKE_PROJECT_TOP_LEVEL_INCLUDES,
before the previous CMAKE_CXX_STANDARD=17 assignment at line 53. MSVC defaults to
C++14, causing protobuf/6.33.5 (which requires C++17) to fail validation on Windows.

Moving the standard declaration above project() ensures conan_provider.cmake always
detects cppstd=17 regardless of platform.

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

Author: leoparente

CMakeLists.txt

@@ -1,5 +1,11 @@
 cmake_minimum_required(VERSION 3.24)
 
+# Must be set before project() so cmake/conan_provider.cmake (loaded via
+# CMAKE_PROJECT_TOP_LEVEL_INCLUDES) sees the correct standard and does not
+# fall back to MSVC's default of C++14 when generating the Conan profile.
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
 #######################################################
 # VERSION
 #######################################################