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/PySound.h

@@ -0,0 +1,76 @@
+#pragma once
+#include "Common.h"
+#include "Python.h"
+
+class PySound;
+
+typedef struct {
+    PyObject_HEAD
+    std::shared_ptr<PySound> data;
+} PySoundObject;
+
+class PySound : public std::enable_shared_from_this<PySound>
+{
+private:
+    sf::SoundBuffer buffer;
+    sf::Sound sound;
+    std::string source;
+    bool loaded;
+
+public:
+    PySound(const std::string& filename);
+
+    // Playback control
+    void play();
+    void pause();
+    void stop();
+
+    // Properties
+    float getVolume() const;
+    void setVolume(float vol);
+    bool getLoop() const;
+    void setLoop(bool loop);
+    bool isPlaying() const;
+    float getDuration() const;
+
+    // Python interface
+    PyObject* pyObject();
+    static PyObject* repr(PyObject* obj);
+    static Py_hash_t hash(PyObject* obj);
+    static int init(PySoundObject* self, PyObject* args, PyObject* kwds);
+    static PyObject* pynew(PyTypeObject* type, PyObject* args, PyObject* kwds);
+
+    // Python methods
+    static PyObject* py_play(PySoundObject* self, PyObject* args);
+    static PyObject* py_pause(PySoundObject* self, PyObject* args);
+    static PyObject* py_stop(PySoundObject* self, PyObject* args);
+
+    // Python getters/setters
+    static PyObject* get_volume(PySoundObject* self, void* closure);
+    static int set_volume(PySoundObject* self, PyObject* value, void* closure);
+    static PyObject* get_loop(PySoundObject* self, void* closure);
+    static int set_loop(PySoundObject* self, PyObject* value, void* closure);
+    static PyObject* get_playing(PySoundObject* self, void* closure);
+    static PyObject* get_duration(PySoundObject* self, void* closure);
+    static PyObject* get_source(PySoundObject* self, void* closure);
+
+    static PyMethodDef methods[];
+    static PyGetSetDef getsetters[];
+};
+
+namespace mcrfpydef {
+    static PyTypeObject PySoundType = {
+        .ob_base = {.ob_base = {.ob_refcnt = 1, .ob_type = NULL}, .ob_size = 0},
+        .tp_name = "mcrfpy.Sound",
+        .tp_basicsize = sizeof(PySoundObject),
+        .tp_itemsize = 0,
+        .tp_repr = PySound::repr,
+        .tp_hash = PySound::hash,
+        .tp_flags = Py_TPFLAGS_DEFAULT,
+        .tp_doc = PyDoc_STR("Sound effect object for short audio clips"),
+        .tp_methods = PySound::methods,
+        .tp_getset = PySound::getsetters,
+        .tp_init = (initproc)PySound::init,
+        .tp_new = PyType_GenericNew,
+    };
+}