Accepting the settings dialog quit the app: with a tray-resident program
"last window closed" must not mean "quit", but QApplication's default
made it so, and on first run the dialog is the only window. Disable
quitOnLastWindowClosed. Also fix listOutputDevices hanging forever
(its callbacks never signalled the PulseAudio main loop), enlarge the
caption window's close button, and add capture-device selection
(enumerated sinks, settings combo, --list-devices/--device) plus model
integrity verification (size + sha256 in the registry, --verify-model and
a "校验完整性" button).
点「确定」后程序自己退出：本程序常驻托盘，"最后一个窗口关闭"不该等于退出，
但 QApplication 默认如此，而首次启动时设置对话框正是唯一窗口。已关闭该默认
行为。同时修复 listOutputDevices 永久卡死（回调没有 signal 主循环）、放大
字幕窗关闭按钮，并新增采集设备选择与模型完整性校验（注册表含 size/sha256，
提供 --verify-model 与设置里的「校验完整性」按钮）。
blumia
0fa0bcb44a