Bump to v1.5.0: cross-lane routing fix, recording double-tap fix, menu reorg

Bug fixes:
* BothIndependent recording was double-tapped — when both WASAPI and
  ASIO outputs were ticked, recordings came out garbled and ~2x the
  expected duration. AudioRecorder now uses four per-lane rings
  (sent-wasapi, sent-asio, recv-wasapi, recv-asio) plus a writer-
  thread mix step that drains min(wasapi, asio) frames and sum-mixes
  with the soft-tanh limiter. Tap signatures gained a RenderRoute
  parameter; Mixed maps to the wasapi slot.
* A peer announcing on the WASAPI lane was inaudible when the
  receiver only had an ASIO output ticked (and vice versa). The
  session opened, samples flowed into the SessionPlayout ring, but
  ReadForRoute(AsioLane) skipped any session whose Route was
  WasapiLane so nothing drained the ring. PlayoutEngine now tracks
  per-lane "is this lane backed by a device" via volatile bools
  settable through SetLaneActive(RenderRoute, bool), called from
  CompositeRenderBackend.SetOutputDevices whenever the device split
  changes. ReadForRoute admits orphan sessions when the other lane
  is inactive.

Menu reorganisation:
* New Options menu (Alt+O) holds Recording settings (Alt+S), Keyboard
  shortcuts (Alt+K, Ctrl+K), Startup behaviour (Alt+T), Preferences
  (Alt+P, Ctrl+P). Pre-v1.5 these were scattered across File menu,
  Record menu, and inside the Preferences dialog itself.
* Record menu mnemonic moved from Alt+O to Alt+K, rendered as
  "Record (Alt+K)" so the chord is visible despite K not being a
  letter in "Record". Alt+R is taken by Receive audio.
* File menu — new Recent profiles submenu (Alt+F, R) listing the
  five most-recently-opened profiles. Press 1..5 inside the submenu
  to jump to a slot. Missing files are skipped from the menu but
  kept in storage.
* Rename current profile moves to Alt+M (was R), Minimise to tray
  moves to Alt+N (was M).
* Lock to audio clock was Alt+K, now Alt+D.

UX additions:
* Ctrl+O = Open profile (matches the menu chord).
* New global hotkey: Start / Stop recording. Pickable from Options
  -> Keyboard shortcuts. Unbound by default. Works system-wide.

Wire format and audio pipeline unchanged from v1.4 — v1.4 and v1.5
peers interoperate.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/RemSound.Core/Profile.cs

@@ -131,6 +131,12 @@ public sealed class Profile
     public HotkeyRecord? TrayHotkey { get; set; }
     public HotkeyRecord? VolumeUpHotkey { get; set; }
     public HotkeyRecord? VolumeDownHotkey { get; set; }
+    /// <summary>Global hotkey for start / stop recording. Toggles the same action as the
+    /// Record menu's "Start recording / Stop recording" item and the in-app Ctrl+R, but
+    /// works system-wide (RemSound doesn't need keyboard focus). Default unset — recording
+    /// is uncommon enough that we don't claim a default chord that might clash with the
+    /// user's other tools.</summary>
+    public HotkeyRecord? ToggleRecordingHotkey { get; set; }
     /// <summary>Hotkey that sends a "raise volume" command to every connected peer that has
     /// "Accept remote volume commands" enabled. The local volume slider on this machine is
     /// NOT touched. Use case: I'm NVDA-Remote'd into another machine and want to nudge the