Release v3.5: USB-card recovery, per-card adaptive buffer, one user folder, audit fixes

- Recover an unplugged/replugged output sound card automatically (issue #5):
  detect the dead WASAPI device and remember the receive-output selection so it
  re-ticks and re-opens when the card returns.
- Adaptive per-card WASAPI buffer target sized to each card's pull chunk, held
  stable so it never flits about under CPU/network load.
- Consolidate all per-user data (config, profiles, logs, sounds) into one
  "user settings and logs" folder; migrate every older layout; exclude it from
  the updater so custom cue sounds now survive updates.
- Mic-privacy detector: warn once when a Windows-blocked mic is switched on, or a
  profile loads with one already on.
- All warning/notice dialogs now come to the foreground even when minimised.
- Apply volume + mute on profile load (were saved but not restored).
- Crash-safe (atomic) profile/config saves.
- Fix two resource leaks (push-mode capture MMDevice; UPnP DeviceFound handler).
- Remove dead code (baseline-diff machinery, dead ASIO probes, no-op stubs).
- Docs: readme.html, MANUAL.md, About-box changelog and release notes for v3.5.

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

src/RemSound.App/ForegroundDialog.cs

@@ -0,0 +1,76 @@
+using System.Drawing;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+
+namespace RemSound.App;
+
+/// <summary>
+/// Shows a dialog FRONT-AND-CENTRE with keyboard focus, WITHOUT disturbing the main window — it can
+/// stay minimised in the tray the whole time. We give the dialog a momentary, top-most, off-taskbar
+/// 1×1 owner window at screen centre and force THAT owner to the foreground (the AttachThreadInput
+/// dance bypasses Windows' focus-stealing lock), so the modal dialog opens on top with focus and a
+/// screen reader lands on it wherever RemSound happens to be sitting. Used for every warning/notice
+/// the app raises (mic-privacy, Realtek, About-after-update, config-moved), so a minimised RemSound
+/// never leaves a blind user with a dialog dinging away behind everything.
+/// </summary>
+internal static class ForegroundDialog
+{
+    /// <summary>Run <paramref name="show"/> with a foreground 1×1 owner; returns its result.</summary>
+    public static T Show<T>(Func<IWin32Window, T> show)
+    {
+        var area = Screen.PrimaryScreen?.WorkingArea ?? new Rectangle(0, 0, 800, 600);
+        using var owner = new Form
+        {
+            ShowInTaskbar = false,
+            FormBorderStyle = FormBorderStyle.None,
+            StartPosition = FormStartPosition.Manual,
+            Size = new Size(1, 1),
+            Location = new Point(area.X + area.Width / 2, area.Y + area.Height / 2),
+            TopMost = true,
+        };
+        owner.Show();
+        ForceForeground(owner.Handle);
+        try { return show(owner); }
+        finally { try { owner.Close(); } catch { /* ignore */ } }
+    }
+
+    /// <summary>Void convenience overload.</summary>
+    public static void Show(Action<IWin32Window> show) =>
+        Show<object?>(owner => { show(owner); return null; });
+
+    /// <summary>Force <paramref name="hWnd"/> to the foreground even when RemSound isn't the active
+    /// app. A plain SetForegroundWindow from a background process is refused by Windows; attaching
+    /// our input queue to the current foreground thread for the call lifts that restriction. The
+    /// owner is top-most regardless, so this is belt-and-braces for focus.</summary>
+    private static void ForceForeground(IntPtr hWnd)
+    {
+        try
+        {
+            var foreThread = GetWindowThreadProcessId(GetForegroundWindow(), out _);
+            var thisThread = GetCurrentThreadId();
+            if (foreThread != 0 && foreThread != thisThread)
+            {
+                AttachThreadInput(foreThread, thisThread, true);
+                try
+                {
+                    BringWindowToTop(hWnd);
+                    SetForegroundWindow(hWnd);
+                }
+                finally { AttachThreadInput(foreThread, thisThread, false); }
+            }
+            else
+            {
+                BringWindowToTop(hWnd);
+                SetForegroundWindow(hWnd);
+            }
+        }
+        catch { /* best-effort; the owner is top-most anyway */ }
+    }
+
+    [DllImport("user32.dll")] private static extern IntPtr GetForegroundWindow();
+    [DllImport("user32.dll")] private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint pid);
+    [DllImport("user32.dll")] private static extern uint GetCurrentThreadId();
+    [DllImport("user32.dll")] private static extern bool AttachThreadInput(uint idAttach, uint idAttachTo, bool fAttach);
+    [DllImport("user32.dll")] private static extern bool SetForegroundWindow(IntPtr hWnd);
+    [DllImport("user32.dll")] private static extern bool BringWindowToTop(IntPtr hWnd);
+}