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/apple/iOS/VoiceCatiOS/SessionState.swift

@@ -27,6 +27,7 @@ struct VoiceState {
     var inputMode: VoiceCatInputMode = .voiceActivation
     var vadThreshold: Float = 0.025
     var inputGain: Float = 1.0
+    var inputNoiseReduction: Bool = false
     var level: Float = 0.0
     var currentDeviceId: String?
     var localStreamId: UInt32 = 0
@@ -353,12 +354,19 @@ final class SessionState {
         UserDefaults.standard.set(gain, forKey: DefaultsKey.inputGain)
     }
 
+    func setInputNoiseReduction(_ on: Bool) {
+        client.setInputNoiseReduction(on)
+        voiceState.inputNoiseReduction = on
+        UserDefaults.standard.set(on, forKey: DefaultsKey.inputNoiseReduction)
+    }
+
     // MARK: - Persisted input settings
 
     private enum DefaultsKey {
         static let inputMode    = "voice.inputMode"
         static let vadThreshold = "voice.vadThreshold"
         static let inputGain    = "voice.inputGain"
+        static let inputNoiseReduction = "voice.inputNoiseReduction"
     }
 
     /// Restore the saved input mode / VAD threshold / mic gain and push them into the core so a
@@ -375,9 +383,13 @@ final class SessionState {
         if d.object(forKey: DefaultsKey.inputGain) != nil {
             voiceState.inputGain = d.float(forKey: DefaultsKey.inputGain)
         }
+        if d.object(forKey: DefaultsKey.inputNoiseReduction) != nil {
+            voiceState.inputNoiseReduction = d.bool(forKey: DefaultsKey.inputNoiseReduction)
+        }
         client.setInputMode(voiceState.inputMode)
         client.setVadThreshold(voiceState.vadThreshold)
         client.setInputGain(voiceState.inputGain)
+        client.setInputNoiseReduction(voiceState.inputNoiseReduction)
     }
 
     private var pttEngaged = false

clients/apple/iOS/VoiceCatiOS/Views/SettingsView.swift

@@ -251,6 +251,13 @@ struct SettingsView: View {
                         .accessibilityLabel("Microphone volume")
                         .accessibilityValue("\(Int((session.voiceState.inputGain * 100).rounded())) percent")
                     }
+
+                    Toggle("Noise Reduction (RNNoise)", isOn: Binding(
+                        get: { session.voiceState.inputNoiseReduction },
+                        set: { session.setInputNoiseReduction($0) }
+                    ))
+                    .accessibilityLabel("Microphone noise reduction")
+                    .accessibilityHint("Denoises your microphone signal for everyone listening.")
                 }
 
                 // MARK: - Notifications