2V1-d: offline login -> select -> loading against a fake 40250 server

port.login_flow drives the real 40250 root scripts through the ported
CPythonNetworkStream and CAccountConnector against a loopback auth + game
server built from net/classic (wire layouts, sequence table, cipher) that
answers like the 40250 desc.cpp/input*.cpp: handshake, key agreement,
LOGIN3/AUTH_SUCCESS, LOGIN2, the character list, DirectEnter reconnect,
CHARACTER_SELECT, the loading packets and CLIENT_VERSION, with every
sequence byte checked.

- NetStream::ActivateCipher decrypts ciphertext already buffered behind
  KEY_AGREEMENT_COMPLETED (PORT)
- CPythonApplication is final (PORT): no application object exists on the
  platform yet, so its virtual overrides must be called directly
- app.GetTime (GetGlobalTime) and camera/center-position stubs
- SendClientVersionPacket verbatim in the PhaseGame stand-in

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

extension/src/port/UserInterface/PythonApplication.h

@@ -42,7 +42,11 @@
 #include "AbstractApplication.h"
 #include "MovieMan.h"
 
-class CPythonApplication : public CMSApplication, public CInputKeyboard, public IAbstractApplication
+// PORT: `final` added. The platform has no CPythonApplication object yet (platform/UserInterface/
+// PythonApplication.cpp), so its members are called on an empty Instance(); `final` lets the compiler
+// call the IAbstractApplication/CMSApplication overrides directly instead of through a vtable that
+// does not exist. Drop it with that note once the application object is constructed.
+class CPythonApplication final : public CMSApplication, public CInputKeyboard, public IAbstractApplication
 {
 	public:
 		enum EDeviceState