feat: Implement comprehensive mouse event system

Implements multiple mouse event improvements for UI elements:

- Mouse enter/exit events (#140): on_enter, on_exit callbacks and
  hovered property for all UIDrawable types (Frame, Caption, Sprite, Grid)
- Headless click events (#111): Track simulated mouse position for
  automation testing in headless mode
- Mouse move events (#141): on_move callback fires continuously while
  mouse is within element bounds
- Grid cell events (#142): on_cell_enter, on_cell_exit, on_cell_click
  callbacks with cell coordinates (x, y), plus hovered_cell property

Includes comprehensive tests for all new functionality.

Closes #140, closes #111, closes #141, closes #142

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

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

src/McRFPy_Automation.h

@@ -51,6 +51,12 @@ public:
     static sf::Keyboard::Key stringToKey(const std::string& keyName);
     static void sleep_ms(int milliseconds);
     
+    // #111 - Simulated mouse position for headless mode
+    static sf::Vector2i getSimulatedMousePosition();
+
 private:
     static GameEngine* getGameEngine();
+
+    // #111 - Track simulated mouse position for headless mode
+    static sf::Vector2i simulated_mouse_pos;
 };