fix: add vcpkg builtin-baseline and properly initialize submodule The build-apps workflow was failing on all vcpkg-dependent jobs (android, windows, macos, ios) because: 1. vcpkg.json was missing the required builtin-baseline commit id 2. The vcpkg submodule was declared in .gitmodules but never initialized Added builtin-baseline to vcpkg.json and properly registered the submodule.