Port route 4-c: NPC shop (PythonShop.cpp) + app cursor state

- UserInterface/PythonShop.cpp ported verbatim (shop module, initshop after initfly);
  pending stub and module stubs removed.
- 40250 PythonApplicationCursor.cpp and SetMouseHandler moved into the platform
  CPythonApplication on file-static members; GetCursorNum out of line, since uishop's
  app.GetCursor() dereferenced the missing application object.
- Fake server: general store (npclist 9003) answers CG_ON_CLICK with GC_SHOP START,
  CG_SHOP BUY/SELL2/END like CShop::Buy / CShopManager::Sell.
- port.login_flow step 10: click the shopkeeper, right-click buy, drag-sell, ESC close.

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

audit/port-map/UserInterface/PythonApplication.cpp.json

@@ -47,7 +47,12 @@
       "status": "TODO"
     },
     "CPythonApplication::SetMouseHandler": {
-      "status": "TODO"
+      "status": "ADAPTED",
+      "impl": [
+        "extension/src/platform/UserInterface/PythonApplication.cpp:SetMouseHandler"
+      ],
+      "note": "Body verbatim on a file-static m_poMouseHandler (no application object yet); SetCursorNum calls its ChangeCursor.",
+      "test": "extension/tests/port_login_flow_test.cpp (step 10)"
     },
     "CPythonApplication::CheckDeviceState": {
       "status": "TODO"