Replace PyObject_GetAttrString with direct type references

Replace ~230 occurrences of PyObject_GetAttrString(McRFPy_API::mcrf_module, "TypeName")
with direct &mcrfpydef::PyXxxType references across 32 source files.

Each PyObject_GetAttrString call returns a new reference. When used inline
in PyObject_IsInstance(), that reference was immediately leaked. When used
for tp_alloc, the reference required careful Py_DECREF management that was
often missing on error paths.

Direct type references are compile-time constants that never need reference
counting, eliminating ~230 potential leak sites and removing ~100 lines of
Py_DECREF/Py_XDECREF cleanup code.

Also adds extractDrawable() helper in UICollection.cpp to replace repeated
8-way type-check-and-extract chains with a single function call.

Closes #267, closes #268

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/PyMusic.cpp

@@ -76,9 +76,8 @@ void PyMusic::setPosition(float pos)
 
 PyObject* PyMusic::pyObject()
 {
-    auto type = (PyTypeObject*)PyObject_GetAttrString(McRFPy_API::mcrf_module, "Music");
+    auto type = &mcrfpydef::PyMusicType;
     PyObject* obj = PyMusic::pynew(type, Py_None, Py_None);
-    Py_DECREF(type);
     try {
         ((PyMusicObject*)obj)->data = shared_from_this();
     }