feat(voice-client): PySide6 desktop client and Windows build scripts

Add voice_confirmation_client (poll, TTS MP3 playback, mic WAV resolve),
PyInstaller spec, start/build helpers, and API unit tests.

Pending manual testing: end-to-end on OR workstations and packaged exe.

Made-with: Cursor

voice_confirmation_client/__main__.py

@@ -0,0 +1,20 @@
+"""Entry: `python -m voice_confirmation_client` or `voice-confirmation-client`."""
+
+from __future__ import annotations
+
+import sys
+
+
+def main() -> None:
+    from PySide6.QtWidgets import QApplication
+
+    from voice_confirmation_client.gui.main_window import MainWindow
+
+    app = QApplication(sys.argv)
+    win = MainWindow()
+    win.show()
+    raise SystemExit(app.exec())
+
+
+if __name__ == "__main__":
+    main()