chatgui: fix rlottie thread hang on Windows shutdown

Root cause: librlottie RleTaskScheduler creates 32 worker threads on first
lottie_animation_from_data call. These pthreads wait in WaitForMultipleObjects(INFINITE)
and never exit. On MinGW, exit()/pthread_join blocks forever.

Changes:
- messagelist: s_icons moved to file-static; cleanupAnimations() clears them,
  calling lottie_animation_destroy BEFORE static destruction
- mainwindow: ~MainWindow calls MessageList::cleanupAnimations() after node stop
- main: ShutdownSentinel counts threads at exit; if >4 remaining, calls
  ExitProcess(0) to bypass CRT pthread_join hang
- main: if rlottie properly shuts down (<=4 threads), normal return (no ExitProcess)

tools/chatgui/src/main.cpp

@@ -5,6 +5,7 @@
 #include <cstdio>
 #ifdef _WIN32
 #include <windows.h>
+#include <tlhelp32.h>
 #endif
 #include "mainwindow.h"
 #include "../db/db_manager.h"
@@ -15,6 +16,19 @@
 #ifdef _WIN32
 static UtunNode* g_ctrl_node = nullptr;
 
+static DWORD count_threads(void) {
+    DWORD pid = GetCurrentProcessId(), count = 0;
+    HANDLE snap = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
+    if (snap == INVALID_HANDLE_VALUE) return 0;
+    THREADENTRY32 te = { sizeof(te) };
+    if (Thread32First(snap, &te)) {
+        do { if (te.th32OwnerProcessID == pid) count++; }
+        while (Thread32Next(snap, &te));
+    }
+    CloseHandle(snap);
+    return count;
+}
+
 static BOOL WINAPI console_ctrl_handler(DWORD dwCtrlType) {
     if (dwCtrlType == CTRL_C_EVENT || dwCtrlType == CTRL_BREAK_EVENT) {
         if (g_ctrl_node) g_ctrl_node->requestStop();
@@ -27,6 +41,14 @@ static BOOL WINAPI console_ctrl_handler(DWORD dwCtrlType) {
 static struct ShutdownSentinel {
     ~ShutdownSentinel() {
         DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "main: static destructors done");
+#ifdef _WIN32
+        DWORD threads = count_threads();
+        DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "main: threads at exit=%lu", (unsigned long)threads);
+        if (threads > 4) {
+            DEBUG_WARN(DEBUG_CATEGORY_DEBUG, "main: %lu hanging threads, ExitProcess", (unsigned long)threads);
+            ExitProcess(0);
+        }
+#endif
     }
 } g_shutdown_sentinel;