feat: Migrate to Python 3.14 (closes #135)

Replace deprecated Python C API calls with modern PyConfig-based initialization:
- PySys_SetArgvEx() -> PyConfig.argv (deprecated since 3.11)
- Py_InspectFlag -> PyConfig.inspect (deprecated since 3.12)

Fix critical memory safety bugs discovered during migration:
- PyColor::from_arg() and PyVector::from_arg() now return new references
  instead of borrowed references, preventing use-after-free when callers
  call Py_DECREF on the result
- GameEngine::testTimers() now holds a local shared_ptr copy during
  callback execution, preventing use-after-free when timer callbacks
  call delTimer() on themselves

Fix double script execution bug with --exec flag:
- Scripts were running twice because GameEngine constructor executed them,
  then main.cpp deleted and recreated the engine
- Now reuses existing engine and just sets auto_exit_after_exec flag

Update test syntax to use keyword arguments for Frame/Caption constructors.

Test results: 127/130 passing (97.7%)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/McRFPy_API.h

@@ -29,8 +29,8 @@ public:
     //static void setSpriteTexture(int);
     inline static GameEngine* game;
     static void api_init();
-    static void api_init(const McRogueFaceConfig& config, int argc, char** argv);
-    static PyStatus init_python_with_config(const McRogueFaceConfig& config, int argc, char** argv);
+    static void api_init(const McRogueFaceConfig& config);
+    static PyStatus init_python_with_config(const McRogueFaceConfig& config);
     static void api_shutdown();
     // Python API functionality - use mcrfpy.* in scripts
     //static PyObject* _drawSprite(PyObject*, PyObject*);