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.Core/ProfileStore.cs

@@ -24,9 +24,9 @@ public sealed class ProfileStore
     public ProfileStore()
     {
         var machineFolder = SanitiseFsName(Environment.MachineName);
-        // 2026-06-07: profiles live under config\profiles\<machine>\ (was <exe>\profiles\<machine>\).
+        // 2026-06-10: profiles live under "user settings and logs"\profiles\<machine>\.
         // AppConfig.MigrateLegacyLayoutIfNeeded moves any pre-existing profiles here at startup.
-        baseDir = Path.Combine(AppContext.BaseDirectory, "config", "profiles", machineFolder);
+        baseDir = Path.Combine(AppConfig.ProfilesBaseDirectory, machineFolder);
         try { Directory.CreateDirectory(baseDir); }
         catch { /* permissions; List/Save will surface this when actually used */ }
     }
@@ -128,7 +128,26 @@ public sealed class ProfileStore
         Directory.CreateDirectory(baseDir);
         var path = PathFor(profile.Title);
         var json = JsonSerializer.Serialize(profile, new JsonSerializerOptions { WriteIndented = true });
-        File.WriteAllText(path, json);
+        WriteFileAtomic(path, json);
+    }
+
+    /// <summary>Write text crash-safely: write a sibling temp file, then atomically move it over the
+    /// target. A crash, power-loss, or the updater force-closing mid-write then leaves either the old
+    /// file or the complete new one — never a truncated file that the catch-all loaders would
+    /// silently read as a blank profile.</summary>
+    private static void WriteFileAtomic(string path, string contents)
+    {
+        var tmp = path + ".tmp";
+        try
+        {
+            File.WriteAllText(tmp, contents);
+            File.Move(tmp, path, overwrite: true);
+        }
+        catch
+        {
+            try { if (File.Exists(tmp)) File.Delete(tmp); } catch { /* ignore */ }
+            throw;
+        }
     }
 
     /// <summary>Deletes the profile by title. Returns true if a file was removed,
@@ -171,7 +190,7 @@ public sealed class ProfileStore
             if (profile is null) return false;
             profile.Title = newTitle;
             var json = JsonSerializer.Serialize(profile, new JsonSerializerOptions { WriteIndented = true });
-            File.WriteAllText(newPath, json);
+            WriteFileAtomic(newPath, json);
             if (!string.Equals(oldPath, newPath, StringComparison.OrdinalIgnoreCase))
             {
                 File.Delete(oldPath);