feat(clients): wire RNNoise mic noise reduction into Windows, macOS, and iOS

Expose the existing send-side vc_set_input_noise_reduction C ABI (MIC-only,
mono, LOCAL — denoises captured mic PCM before input gain and VAD/PTT gate)
as a persisted global toggle in each client's audio settings, applied live
and re-applied on Join Voice. Mirrors the existing mic-gain wiring pattern.

- Shared Swift (VoiceCatCore): add setInputNoiseReduction(_:) wrapper
- Windows: P/Invoke + SetInputNoiseReduction wrapper, MicNoiseReduction in
  VoiceSettings, new checkbox in AudioSettingsForm (layout shifted +28px),
  apply on Join Voice; also fix stale 'planned - currently passthrough'
  label on the receive-side per-user NR checkbox (RNNoise now backs it)
- macOS: inputNoiseReduction state + UserDefaults in MainWindowController,
  NR checkbox + nrChanged action in SettingsWindowController
- iOS: inputNoiseReduction in VoiceState + setter + restore in SessionState,
  NR Toggle in SettingsView Voice section

Aux/screen are out of scope by design (core's NR guards kind == MIC). Apple
builds require a rebuilt VoiceCatCore.xcframework with VOICECAT_HAS_NS.

clients/windows/VoiceCat.Interop/NativeMethods.cs

@@ -83,6 +83,9 @@ internal static partial class NativeMethods
     [LibraryImport(LibName)]
     internal static partial VcResult vc_set_input_gain(nint c, float gain);
 
+    [LibraryImport(LibName)]
+    internal static partial VcResult vc_set_input_noise_reduction(nint c, int enable);
+
     [LibraryImport(LibName)]
     internal static partial VcResult vc_set_remote_stream(nint c, uint userId, uint streamId,
         float gain, int muted, int noiseReduction);

clients/windows/VoiceCat.Interop/VoiceCatClient.cs

@@ -232,6 +232,13 @@ public sealed class VoiceCatClient : IDisposable
     public VcResult SetInputGain(float gain) =>
         NativeMethods.vc_set_input_gain(_handle.DangerousGetHandle(), gain < 0f ? 0f : gain);
 
+    /// <summary>Send-side microphone noise suppression (RNNoise). Denoises captured MIC PCM before
+    /// the input gain and VAD/PTT gate, so everyone hears the cleaned signal. MIC stream only,
+    /// mono only; always LOCAL — no protocol traffic. Independent of per-listener receive-side
+    /// NR in <see cref="SetRemoteStream"/>.</summary>
+    public VcResult SetInputNoiseReduction(bool enable) =>
+        NativeMethods.vc_set_input_noise_reduction(_handle.DangerousGetHandle(), enable ? 1 : 0);
+
     public VcResult SetRemoteStream(uint userId, uint streamId, float gain, bool muted, bool noiseReduction) =>
         NativeMethods.vc_set_remote_stream(_handle.DangerousGetHandle(), userId, streamId, gain,
             muted ? 1 : 0, noiseReduction ? 1 : 0);