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

build_voice_confirmation_client.bat

@@ -0,0 +1,30 @@
+@echo off
+REM 在 Windows 上将语音确认客户端打成 PyInstaller 目录包（内含 .exe）。
+REM 需在仓库根目录双击运行，或在 cmd 中执行；首次会自动 uv sync。
+REM 可选：build_voice_confirmation_client.bat --clean  （先清空 build、dist）
+
+setlocal EnableExtensions
+cd /d "%~dp0"
+
+echo [1/2] uv sync --group voice-client-build
+uv sync --group voice-client-build
+if errorlevel 1 goto :failed
+
+echo [2/2] PyInstaller ^(voice_client.spec^)
+if /i "%~1"=="--clean" (
+  uv run --group voice-client-build python scripts\build_voice_client.py --clean
+) else (
+  uv run --group voice-client-build python scripts\build_voice_client.py
+)
+if errorlevel 1 goto :failed
+
+echo.
+echo 完成。输出目录: %CD%\dist\voice-confirmation-client\
+echo 主程序: dist\voice-confirmation-client\voice-confirmation-client.exe
+pause
+exit /b 0
+
+:failed
+echo 构建失败（见上方日志）。
+pause
+exit /b 1