fix(core): apply core 64-bit and thread stability fixes

[fbraz3]

Objective

Apply critical core 64-bit & thread stability fixes discovered during the online services investigation.

Summary of Changes

This PR incorporates 4 independent stability and compatibility fixes onto main:

1. System Timer 64-Bit Truncation (systimer.h):

   • Updates systimerGetMS(), SysTimeClass::Get(), and internal members (StartTime, WrapAdd) to explicit unsigned int return/variable types.
   • Prevents LP64 64-bit integer truncation when TIMEGETTIME values are stored in 32-bit unsigned int variables, resolving premature ThreadClass::Stop() timeouts and shutdown segfaults.

2. GadgetListBox 64-Bit Pointer Truncation (GadgetListBox.cpp):

   • Fixed multi-selection handling in GadgetListBoxSystem for GLM_GET_SELECTION message.
   • Casts mData2 to Int** to properly pass internal 64-bit list->selections pointer without truncating bits.

3. POSIX Thread Cancellation Exception Handling (abi::__forced_unwind):

   • Added #if defined(_UNIX) && !defined(__APPLE__) guarded catch (abi::__forced_unwind&) { throw; } blocks before catch (...) in GameSpy worker thread loops (BuddyThread, GameResultsThread, PeerThread, PersistentStorageThread, PingThread).
   • Ensures clean thread unwinding on Linux GCC/Clang while guarding against missing abi::__forced_unwind on macOS libc++.

4. Linux Deployment Scripts Static Library Check (deploy-linux.sh / deploy-linux-zh.sh):

   • Guarded runtime library check for libavcodec.so using ldd "${BINARY_SRC}" | grep -q "libavcodec.so".
   • Prevents script failure when FFmpeg is statically linked.

Commits Included

• b810340b1 fix(core): resolve 64-bit truncation bug in system timer
• 5bae35508 fix(ui): fix pointer truncation in GadgetListBox GetSelection for 64-bit systems
• 41bebcb08 fix(network): rethrow abi::__forced_unwind in GameSpy threads
• 2e40f523d fix(deploy): handle static FFmpeg linkage gracefully in Linux deploy scripts

Verification

• Built and configured cleanly using cmake --preset macos-vulkan.