Service: config dialog + Service menu

Local checkpoint - NOT for public release.

- ServiceProfileDialog: modal 3-tab editor (Audio send / Audio profile / Connectivity)
  reusing the house controls, with a Save and Close / Cancel / Additional options
  button row. Send-only: send-mode chooser + WASAPI outputs/apps + inputs (no "Send
  my audio" toggle, no receive, no ASIO); codec/rate/lock-to-clock; peers add/remove +
  a Set password button. Additional options sub-dialog = play connect/disconnect sound
  + enable service logging. Edits a Profile clone; returns it on OK.
- Service menu in MainForm: status line + Configure / Install / Uninstall / Start / Stop,
  items enabled per live state on drop-down. Install/uninstall confirm then elevate.
  Configure saves the reserved service profile, points AppConfig at it, stores the
  machine-wide logging choice, and restarts a running service to pick up edits.
- ProfileStore.ReservedServiceProfileTitle ("RemSound service"): the service profile
  lives with normal profiles (so the service Loads it) but ListProfileTitles hides it
  from every picker. ServiceControl reuses that single constant.
- Self-test: the service dialog is now in the accessibility audit (constructs cleanly,
  unique mnemonics, all controls named). Gate 20/20.

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

src/RemSound.Core/ProfileStore.cs

@@ -49,9 +49,14 @@ public sealed class ProfileStore
     /// <summary>Folder this store reads from and writes into.</summary>
     public string BaseDirectory => baseDir;
 
+    /// <summary>Reserved title of the send-only Windows service's profile. It lives in the same folder
+    /// as normal profiles (so the service loads it via <see cref="Load"/>), but it's edited only through
+    /// the Service menu's config dialog and hidden from the normal picker by <see cref="ListProfileTitles"/>.</summary>
+    public const string ReservedServiceProfileTitle = "RemSound service";
+
     /// <summary>Returns the user-facing titles of every profile in the folder, sorted
-    /// alphabetically (case-insensitive). Excludes the synthetic blank-template; the
-    /// caller decides whether to surface that.</summary>
+    /// alphabetically (case-insensitive). Excludes the synthetic blank-template and the reserved
+    /// service profile; the caller decides whether to surface the blank template.</summary>
     public IReadOnlyList<string> ListProfileTitles()
     {
         if (!Directory.Exists(baseDir)) return [];
@@ -60,6 +65,7 @@ public sealed class ProfileStore
             return Directory.GetFiles(baseDir, "*.json")
                 .Select(p => TryReadTitle(p) ?? Path.GetFileNameWithoutExtension(p))
                 .Where(static t => !string.IsNullOrWhiteSpace(t))
+                .Where(static t => !string.Equals(t, ReservedServiceProfileTitle, StringComparison.OrdinalIgnoreCase))
                 .OrderBy(t => t, StringComparer.OrdinalIgnoreCase)
                 .ToList();
         }