fix(windows): statically link MinGW runtime into all binaries

The static-MinGW recipe (-static-libgcc -static-libstdc++ -static) was
only applied inside the VOICECAT_BUILD_SHARED branch in core/CMakeLists,
so it covered voicecat.dll but not voicecat-server.exe / vccli. With the
x64-mingw-static triplet only vcpkg's own deps are static; the GCC/MinGW
runtime stays dynamic, so the server failed to start on clean Windows
machines with missing libgcc_s_seh-1.dll / libwinpthread-1.dll /
libstdc++-6.dll.

Move the recipe to a global add_link_options (WIN32 AND MINGW) so every
produced binary embeds the runtime. Verified with objdump -p: only
Windows system DLLs remain.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CMakeLists.txt

@@ -37,6 +37,20 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 
+# ── Static MinGW runtime (Windows) ────────────────────────────────────────────
+# x64-mingw-static only statically links vcpkg's OWN deps (protobuf, sodium, ...);
+# the GCC/MinGW runtime stays dynamic by default, so every produced .exe/.dll
+# otherwise depends on libgcc_s_seh-1.dll / libwinpthread-1.dll / libstdc++-6.dll
+# at runtime — DLLs that exist on a dev box (MSYS2/UCRT64) but not on a clean
+# Windows machine, where the server then fails to start with "… was not found".
+# Apply the fully-static-MinGW recipe to ALL targets so binaries are portable.
+# (The SHARED voicecat.dll already sets these in core/CMakeLists.txt; the duplicate
+# is harmless. Verify with: objdump -p build/<preset>/bin/voicecat-server.exe |
+# grep "DLL Name" — only Windows system DLLs should remain.)
+if(WIN32 AND MINGW)
+    add_link_options(-static-libgcc -static-libstdc++ -static -lwinpthread)
+endif()
+
 # ── Targets ───────────────────────────────────────────────────────────────────
 add_subdirectory(core)