v4.1: two screen-reader fixes — silent start-in-tray, announce on restore

- Starting straight into the tray (StartMinimised / --minimized) no longer plays the "minimise"
  cue; only a genuine user minimise does (the startup path passes playCue:false)
- Restoring the window from the tray now lands focus on a real named control on the active tab so
  NVDA announces it, instead of resting on the role-less QuietTabControl and surfacing silently
- Shared the focus-a-leaf-for-announcement helper between the main window and Preferences

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/MainFormTrayController.cs

@@ -227,13 +227,17 @@ internal sealed class MainFormTrayController : IDisposable
     [return: MarshalAs(UnmanagedType.Bool)]
     private static extern bool SetForegroundWindow(IntPtr hWnd);
 
-    public void Minimize()
+    /// <summary>Hide the window to the tray. <paramref name="playCue"/> defaults true for a genuine
+    /// user-initiated minimise; the startup-minimise path passes false because that's not the user
+    /// choosing to hide the window — and the usual "was it visible?" guard can't tell the two apart,
+    /// since by the time the deferred startup minimise runs the window HAS been shown (Visible=true).</summary>
+    public void Minimize(bool playCue = true)
     {
-        // Only sound the "hide" cue on a genuine shown -> hidden transition (not a startup-minimise
-        // before the window has ever been shown, nor a repeat call once already hidden).
+        // Only sound the "hide" cue on a genuine shown -> hidden transition the user asked for: not a
+        // startup-minimise (playCue:false), and not a repeat call once already hidden (wasVisible).
         var wasVisible = owner.Visible;
         owner.Hide();
-        if (wasVisible) (owner as MainForm)?.PlayWindowVisibilityCue(show: false);
+        if (wasVisible && playCue) (owner as MainForm)?.PlayWindowVisibilityCue(show: false);
         // Refresh the tooltip BEFORE showing the icon so the shell's NIM_ADD call carries
         // the current live state (peer count, send / receive routing, recording timer),
         // not a stale "starting up" string set earlier. The shell tends to cache hover