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/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