drop ossp-uuid dependency linux/archlinux

[gorsing]

Remove external ossp-uuid dependency

• Replace OSSP UUID library with built-in C++ generator
• UUID v4 format is preserved (version/variant bits correct)
• Code is now identical across all platforms (Linux, macOS, Windows)
• Removes need to install ossp-uuid from AUR on Arch Linux

CMakeLists.txt: drop OSSPUUID pkg_search_module, link, and include
UUID.h: remove <uuid.h> include and UUID_MAKE_V4 define
UUID.cpp: replace uuid_create/uuid_make/uuid_export with std::mt19937