fix: tray main-thread message loop, numpy <2.0 pin, installer config copy

- Rewrite tray to run on main thread (pystray owns message loop, uvicorn
  in background thread) — fixes unresponsive confirmation dialogs
- Use native Windows MessageBoxW instead of tkinter (embedded Python
  has no tkinter)
- Pin numpy <2.0 to fix soundcard's numpy.fromstring (removed in 2.0)
- Strip transitive numpy 2.x wheels in build script
- Installer copies config.example.yaml as config.yaml on fresh install
- Suppress noisy screen_brightness_control warnings

installer.nsi

@@ -73,6 +73,10 @@ Section "!Core (required)" SecCore
     ; Copy entire distribution
     File /r "dist\media-server\*.*"
 
+    ; Create config.yaml from example if it doesn't already exist (preserve user config on upgrade)
+    IfFileExists "$INSTDIR\config.yaml" +2
+    CopyFiles /SILENT "$INSTDIR\config.example.yaml" "$INSTDIR\config.yaml"
+
     ; Create uninstaller
     WriteUninstaller "$INSTDIR\uninstall.exe"