feat: Add Sound/Music classes, keyboard state, version (#66, #160, #164)

Replace module-level audio functions with proper OOP API:
- mcrfpy.Sound: Wraps sf::SoundBuffer + sf::Sound for short effects
- mcrfpy.Music: Wraps sf::Music for streaming long tracks
- Both support: volume, loop, playing, duration, play/pause/stop
- Music adds position property for seeking

Add mcrfpy.keyboard singleton for real-time modifier state:
- shift, ctrl, alt, system properties (bool, read-only)
- Queries sf::Keyboard::isKeyPressed() directly

Add mcrfpy.__version__ = "1.0.0" for version identity

Remove old audio API entirely (no deprecation - unused in codebase):
- createSoundBuffer, loadMusic, playSound
- setMusicVolume, getMusicVolume, setSoundVolume, getSoundVolume

closes #66, closes #160, closes #164

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/McRFPy_API.h

@@ -37,19 +37,6 @@ public:
     static void REPL_device(FILE * fp, const char *filename);
     static void REPL();
 
-    static std::vector<sf::SoundBuffer>* soundbuffers;
-    static sf::Music* music;
-    static sf::Sound* sfx;
-    
-    
-    static PyObject* _createSoundBuffer(PyObject*, PyObject*);
-    static PyObject* _loadMusic(PyObject*, PyObject*);
-    static PyObject* _setMusicVolume(PyObject*, PyObject*);
-    static PyObject* _setSoundVolume(PyObject*, PyObject*);
-    static PyObject* _playSound(PyObject*, PyObject*);
-    static PyObject* _getMusicVolume(PyObject*, PyObject*);
-    static PyObject* _getSoundVolume(PyObject*, PyObject*);
-    
     static PyObject* _sceneUI(PyObject*, PyObject*);
 
     // scene control