fix(cleanup): clear global enum-wrapper registry before tearing down class infos

ASan reported a heap-use-after-free during teardown: the global registry
of top-level enum wrappers held raw pointers to `PythonQtClassInfo` that
were deleted in `~PythonQtPrivate()`. Subsequent lookups (e.g., triggered
by late attribute access) read freed memory.

- Add `PythonQtClassInfo::clearGlobalNamespaceWrappers()`
- Call it in `~PythonQtPrivate()` before `qDeleteAll(_knownClassInfos)`
- Explicitly clear `_knownClassInfos` after deletion to avoid stale entries

Author: jcfr

src/PythonQt.cpp

@@ -421,9 +421,10 @@ PythonQtPrivate::~PythonQtPrivate() {
   delete _defaultImporter;
   _defaultImporter = nullptr;
 
-  {
-    qDeleteAll(_knownClassInfos);
-  }
+  PythonQtClassInfo::clearGlobalNamespaceWrappers();
+
+  qDeleteAll(_knownClassInfos);
+  _knownClassInfos.clear();
 
   PythonQtMethodInfo::cleanupCachedMethodInfos();
   PythonQtArgumentFrame::cleanupFreeList();

src/PythonQtClassInfo.cpp

@@ -1043,6 +1043,11 @@ void PythonQtClassInfo::addGlobalNamespaceWrapper(PythonQtClassInfo* namespaceWr
   _globalNamespaceWrappers.insert(0, namespaceWrapper);
 }
 
+void PythonQtClassInfo::clearGlobalNamespaceWrappers()
+{
+  _globalNamespaceWrappers.clear();
+}
+
 void PythonQtClassInfo::updateRefCountingCBs()
 {
   if (!_refCallback) {

src/PythonQtClassInfo.h

@@ -244,6 +244,10 @@ class PYTHONQT_EXPORT PythonQtClassInfo {
   //! Add a wrapper that contains global enums
   static void addGlobalNamespaceWrapper(PythonQtClassInfo* namespaceWrapper);
 
+  //! Clear the registry of global-namespace wrappers (used for top-level enums).
+  //! Must be called before destroying PythonQtClassInfo instances and before a fresh init.
+  static void clearGlobalNamespaceWrappers();
+
 private:
   void updateRefCountingCBs();