v1.1.3: Brickwall limiter + double-click reset on all knobs

- Output brickwall limiter (0 dB ceiling) with toggle in master row
- All sliders reset to default on double-click:
  Master gain → 0 dB, Freq → 1000 Hz, Gain → 0 dB, Q → 1.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Source/PluginProcessor.h

@@ -43,6 +43,7 @@ public:
     // Settings
     std::atomic<bool> bypassed { false };
     std::atomic<float> masterGainDb { 0.0f };
+    std::atomic<bool> limiterEnabled { true };
 
     void setQuality (int fftOrder);
 
@@ -55,6 +56,7 @@ private:
 
     FIREngine firEngine;
     juce::dsp::Convolution convolution;
+    juce::dsp::Limiter<float> limiter;
 
     double currentSampleRate = 44100.0;
     int currentBlockSize = 512;